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<div class="section" id="zcml-directives">
<h1>ZCML directives<a class="headerlink" href="#zcml-directives" title="Permalink to this headline">¶</a></h1>
<p>Components may be registered using the registration API exposed by
<tt class="docutils literal"><span class="pre">zope.component</span></tt> (provideAdapter, provideUtility, etc.). They may
also be registered using configuration files. The common way to do
that is by using ZCML (Zope Configuration Markup Language), an XML
spelling of component registration.</p>
<p>In ZCML, each XML element is a <em>directive</em>. There are different
top-level directives that let us register components. We will
introduce them one by one here.</p>
<p>This helper will let us easily execute ZCML snippets:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">cStringIO</span> <span class="kn">import</span> <span class="n">StringIO</span>
<span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.configuration.xmlconfig</span> <span class="kn">import</span> <span class="n">xmlconfig</span>
<span class="gp">>>> </span><span class="k">def</span> <span class="nf">runSnippet</span><span class="p">(</span><span class="n">snippet</span><span class="p">):</span>
<span class="gp">... </span> <span class="n">template</span> <span class="o">=</span> <span class="s">"""</span><span class="se">\</span>
<span class="gp">... </span><span class="s"> <configure xmlns='http://namespaces.zope.org/zope'</span>
<span class="gp">... </span><span class="s"> i18n_domain="zope"></span>
<span class="gp">... </span><span class="s"> </span><span class="si">%s</span><span class="s"></span>
<span class="gp">... </span><span class="s"> </configure>"""</span>
<span class="gp">... </span> <span class="n">xmlconfig</span><span class="p">(</span><span class="n">StringIO</span><span class="p">(</span><span class="n">template</span> <span class="o">%</span> <span class="n">snippet</span><span class="p">))</span>
</pre></div>
</div>
<div class="section" id="adapter">
<h2>adapter<a class="headerlink" href="#adapter" title="Permalink to this headline">¶</a></h2>
<p>Adapters play a key role in the Component Architecture. In ZCML, they
are registered with the <adapter /> directive.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.component.testfiles.adapter</span> <span class="kn">import</span> <span class="n">A1</span><span class="p">,</span> <span class="n">A2</span><span class="p">,</span> <span class="n">A3</span><span class="p">,</span> <span class="n">Handler</span>
<span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.component.testfiles.adapter</span> <span class="kn">import</span> <span class="n">I1</span><span class="p">,</span> <span class="n">I2</span><span class="p">,</span> <span class="n">I3</span><span class="p">,</span> <span class="n">IS</span>
<span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.component.testfiles.components</span> <span class="kn">import</span> <span class="n">IContent</span><span class="p">,</span> <span class="n">Content</span><span class="p">,</span> <span class="n">Comp</span><span class="p">,</span> <span class="n">comp</span>
</pre></div>
</div>
<p>Before we register the first test adapter, we can verify that adapter
lookup doesn’t work yet:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.component.tests.examples</span> <span class="kn">import</span> <span class="n">clearZCML</span>
<span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.component.testfiles.components</span> <span class="kn">import</span> <span class="n">IApp</span>
<span class="gp">>>> </span><span class="n">IApp</span><span class="p">(</span><span class="n">Content</span><span class="p">(),</span> <span class="bp">None</span><span class="p">)</span> <span class="ow">is</span> <span class="bp">None</span>
<span class="go">True</span>
</pre></div>
</div>
<p>Then we register the adapter and see that the lookup works:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.components.Comp"</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.components.IApp"</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">IApp</span><span class="p">(</span><span class="n">Content</span><span class="p">())</span><span class="o">.</span><span class="n">__class__</span>
<span class="go"><class 'zope.component.testfiles.components.Comp'></span>
</pre></div>
</div>
<p>It is also possible to give adapters names. Then the combination of
required interface, provided interface and name makes the adapter
lookup unique. The name is supplied using the <tt class="docutils literal"><span class="pre">name</span></tt> argument to
the <adapter /> directive:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.component.tests.examples</span> <span class="kn">import</span> <span class="n">clearZCML</span>
<span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="kn">import</span> <span class="nn">zope.component</span>
<span class="gp">>>> </span><span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">queryAdapter</span><span class="p">(</span><span class="n">Content</span><span class="p">(),</span> <span class="n">IApp</span><span class="p">,</span> <span class="s">'test'</span><span class="p">)</span> <span class="ow">is</span> <span class="bp">None</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.components.Comp"</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.components.IApp"</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent"</span>
<span class="gp">... </span><span class="s"> name="test"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">getAdapter</span><span class="p">(</span><span class="n">Content</span><span class="p">(),</span> <span class="n">IApp</span><span class="p">,</span> <span class="s">'test'</span><span class="p">)</span><span class="o">.</span><span class="n">__class__</span>
<span class="go"><class 'zope.component.testfiles.components.Comp'></span>
</pre></div>
</div>
<div class="section" id="adapter-factories">
<h3>Adapter factories<a class="headerlink" href="#adapter-factories" title="Permalink to this headline">¶</a></h3>
<p>It is possible to supply more than one adapter factory. In this case,
during adapter lookup each factory will be called and the return value
will be given to the next factory. The return value of the last
factory is returned as the result of the adapter lookup. For examle:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A1</span>
<span class="gp">... </span><span class="s"> zope.component.testfiles.adapter.A2</span>
<span class="gp">... </span><span class="s"> zope.component.testfiles.adapter.A3"</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.components.IApp"</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
</pre></div>
</div>
<p>The resulting adapter is an A3, around an A2, around an A1, around the
adapted object:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">content</span> <span class="o">=</span> <span class="n">Content</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">a3</span> <span class="o">=</span> <span class="n">IApp</span><span class="p">(</span><span class="n">content</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a3</span><span class="o">.</span><span class="n">__class__</span> <span class="ow">is</span> <span class="n">A3</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">a2</span> <span class="o">=</span> <span class="n">a3</span><span class="o">.</span><span class="n">context</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
<span class="gp">>>> </span><span class="n">a2</span><span class="o">.</span><span class="n">__class__</span> <span class="ow">is</span> <span class="n">A2</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">a1</span> <span class="o">=</span> <span class="n">a2</span><span class="o">.</span><span class="n">context</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
<span class="gp">>>> </span><span class="n">a1</span><span class="o">.</span><span class="n">__class__</span> <span class="ow">is</span> <span class="n">A1</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">a1</span><span class="o">.</span><span class="n">context</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="ow">is</span> <span class="n">content</span>
<span class="go">True</span>
</pre></div>
</div>
<p>Of course, if no factory is provided at all, we will get an error:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> factory=""</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.components.IApp"</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gt">Traceback (most recent call last):</span>
<span class="c">...</span>
<span class="gr">ZopeXMLConfigurationError</span>: <span class="n">File "<string>", line 4.2-8.8</span>
<span class="go"> ValueError: No factory specified</span>
</pre></div>
</div>
</div>
<div class="section" id="declaring-for-and-provides-in-python">
<h3>Declaring <tt class="docutils literal"><span class="pre">for</span></tt> and <tt class="docutils literal"><span class="pre">provides</span></tt> in Python<a class="headerlink" href="#declaring-for-and-provides-in-python" title="Permalink to this headline">¶</a></h3>
<p>The <adapter /> directive can figure out from the in-line Python
declaration (using <tt class="docutils literal"><span class="pre">zope.component.adapts()</span></tt> or
<tt class="docutils literal"><span class="pre">zope.component.adapter()</span></tt> as well as <tt class="docutils literal"><span class="pre">zope.interface.implements</span></tt>)
what the adapter should be registered for and what it provides:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">IApp</span><span class="p">(</span><span class="n">Content</span><span class="p">(),</span> <span class="bp">None</span><span class="p">)</span> <span class="ow">is</span> <span class="bp">None</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter factory="zope.component.testfiles.components.Comp" />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">IApp</span><span class="p">(</span><span class="n">Content</span><span class="p">())</span><span class="o">.</span><span class="n">__class__</span>
<span class="go"><class 'zope.component.testfiles.components.Comp'></span>
</pre></div>
</div>
<p>Of course, if the adapter has no <tt class="docutils literal"><span class="pre">implements()</span></tt> declaration, ZCML
can’t figure out what it provides:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A4"</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gt">Traceback (most recent call last):</span>
<span class="c">...</span>
<span class="gr">ZopeXMLConfigurationError</span>: <span class="n">File "<string>", line 4.2-7.8</span>
<span class="go"> TypeError: Missing 'provides' attribute</span>
</pre></div>
</div>
<p>On the other hand, if the factory implements more than one interface,
ZCML can’t figure out what it should provide either:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A5"</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gt">Traceback (most recent call last):</span>
<span class="c">...</span>
<span class="gr">ZopeXMLConfigurationError</span>: <span class="n">File "<string>", line 4.2-7.8</span>
<span class="go"> TypeError: Missing 'provides' attribute</span>
</pre></div>
</div>
<p>A not so common edge case is registering adapters directly for
classes, not for interfaces. For example:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.Content"</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.adapter.I1"</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A1"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">content</span> <span class="o">=</span> <span class="n">Content</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">a1</span> <span class="o">=</span> <span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">getAdapter</span><span class="p">(</span><span class="n">content</span><span class="p">,</span> <span class="n">I1</span><span class="p">,</span> <span class="s">''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="nb">isinstance</span><span class="p">(</span><span class="n">a1</span><span class="p">,</span> <span class="n">A1</span><span class="p">)</span>
<span class="go">True</span>
</pre></div>
</div>
<p>This time, any object providing <tt class="docutils literal"><span class="pre">IContent</span></tt> won’t work if it’s not an
instance of the <tt class="docutils literal"><span class="pre">Content</span></tt> class:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">zope.interface</span>
<span class="gp">>>> </span><span class="k">class</span> <span class="nc">MyContent</span><span class="p">:</span>
<span class="gp">... </span> <span class="n">zope</span><span class="o">.</span><span class="n">interface</span><span class="o">.</span><span class="n">implements</span><span class="p">(</span><span class="n">IContent</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">getAdapter</span><span class="p">(</span><span class="n">MyContent</span><span class="p">(),</span> <span class="n">I1</span><span class="p">,</span> <span class="s">''</span><span class="p">)</span>
<span class="gt">Traceback (most recent call last):</span>
<span class="c">...</span>
<span class="gr">ComponentLookupError</span>: <span class="n">...</span>
</pre></div>
</div>
</div>
<div class="section" id="multi-adapters">
<h3>Multi-adapters<a class="headerlink" href="#multi-adapters" title="Permalink to this headline">¶</a></h3>
<p>Conventional adapters adapt one object to provide another interface.
Multi-adapters adapt several objects at once:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent</span>
<span class="gp">... </span><span class="s"> zope.component.testfiles.adapter.I1</span>
<span class="gp">... </span><span class="s"> zope.component.testfiles.adapter.I2"</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.adapter.I3"</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A3"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">content</span> <span class="o">=</span> <span class="n">Content</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">a1</span> <span class="o">=</span> <span class="n">A1</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">a2</span> <span class="o">=</span> <span class="n">A2</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">a3</span> <span class="o">=</span> <span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">queryMultiAdapter</span><span class="p">((</span><span class="n">content</span><span class="p">,</span> <span class="n">a1</span><span class="p">,</span> <span class="n">a2</span><span class="p">),</span> <span class="n">I3</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a3</span><span class="o">.</span><span class="n">__class__</span> <span class="ow">is</span> <span class="n">A3</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">a3</span><span class="o">.</span><span class="n">context</span> <span class="o">==</span> <span class="p">(</span><span class="n">content</span><span class="p">,</span> <span class="n">a1</span><span class="p">,</span> <span class="n">a2</span><span class="p">)</span>
<span class="go">True</span>
</pre></div>
</div>
<p>You can even adapt an empty list of objects (we call this a
null-adapter):</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> for=""</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.adapter.I3"</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A3"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a3</span> <span class="o">=</span> <span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">queryMultiAdapter</span><span class="p">((),</span> <span class="n">I3</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a3</span><span class="o">.</span><span class="n">__class__</span> <span class="ow">is</span> <span class="n">A3</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">a3</span><span class="o">.</span><span class="n">context</span> <span class="o">==</span> <span class="p">()</span>
<span class="go">True</span>
</pre></div>
</div>
<p>Even with multi-adapters, ZCML can figure out the <tt class="docutils literal"><span class="pre">for</span></tt> and
<tt class="docutils literal"><span class="pre">provides</span></tt> parameters from the Python declarations:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter factory="zope.component.testfiles.adapter.A3" />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a3</span> <span class="o">=</span> <span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">queryMultiAdapter</span><span class="p">((</span><span class="n">content</span><span class="p">,</span> <span class="n">a1</span><span class="p">,</span> <span class="n">a2</span><span class="p">),</span> <span class="n">I3</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a3</span><span class="o">.</span><span class="n">__class__</span> <span class="ow">is</span> <span class="n">A3</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">a3</span><span class="o">.</span><span class="n">context</span> <span class="o">==</span> <span class="p">(</span><span class="n">content</span><span class="p">,</span> <span class="n">a1</span><span class="p">,</span> <span class="n">a2</span><span class="p">)</span>
<span class="go">True</span>
</pre></div>
</div>
<p>Chained factories are not supported for multi-adapters, though:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent</span>
<span class="gp">... </span><span class="s"> zope.component.testfiles.adapter.I1</span>
<span class="gp">... </span><span class="s"> zope.component.testfiles.adapter.I2"</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.components.IApp"</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A1</span>
<span class="gp">... </span><span class="s"> zope.component.testfiles.adapter.A2"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gt">Traceback (most recent call last):</span>
<span class="c">...</span>
<span class="gr">ZopeXMLConfigurationError</span>: <span class="n">File "<string>", line 4.2-11.8</span>
<span class="go"> ValueError: Can't use multiple factories and multiple for</span>
</pre></div>
</div>
<p>And neither for null-adapters:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> for=""</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.components.IApp"</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A1</span>
<span class="gp">... </span><span class="s"> zope.component.testfiles.adapter.A2"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gt">Traceback (most recent call last):</span>
<span class="c">...</span>
<span class="gr">ZopeXMLConfigurationError</span>: <span class="n">File "<string>", line 4.2-9.8</span>
<span class="go"> ValueError: Can't use multiple factories and multiple for</span>
</pre></div>
</div>
</div>
<div class="section" id="protected-adapters">
<h3>Protected adapters<a class="headerlink" href="#protected-adapters" title="Permalink to this headline">¶</a></h3>
<p>Adapters can be protected with a permission. First we have to define
a permission for which we’ll have to register the <permission />
directive:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">IApp</span><span class="p">(</span><span class="n">Content</span><span class="p">(),</span> <span class="bp">None</span><span class="p">)</span> <span class="ow">is</span> <span class="bp">None</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="kn">import</span> <span class="nn">zope.security</span>
<span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.configuration.xmlconfig</span> <span class="kn">import</span> <span class="n">XMLConfig</span>
<span class="gp">>>> </span><span class="n">XMLConfig</span><span class="p">(</span><span class="s">'meta.zcml'</span><span class="p">,</span> <span class="n">zope</span><span class="o">.</span><span class="n">security</span><span class="p">)()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <permission</span>
<span class="gp">... </span><span class="s"> id="y.x"</span>
<span class="gp">... </span><span class="s"> title="XY"</span>
<span class="gp">... </span><span class="s"> description="Allow XY."</span>
<span class="gp">... </span><span class="s"> /></span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.components.Comp"</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.components.IApp"</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent"</span>
<span class="gp">... </span><span class="s"> permission="y.x"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
</pre></div>
</div>
<p>We see that the adapter is a location proxy now so that the
appropriate permissions can be found from the context:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">IApp</span><span class="p">(</span><span class="n">Content</span><span class="p">())</span><span class="o">.</span><span class="n">__class__</span>
<span class="go"><class 'zope.component.testfiles.components.Comp'></span>
<span class="gp">>>> </span><span class="nb">type</span><span class="p">(</span><span class="n">IApp</span><span class="p">(</span><span class="n">Content</span><span class="p">()))</span>
<span class="go"><class 'zope.location.location.LocationProxy'></span>
</pre></div>
</div>
<p>We can also go about it a different way. Let’s make a public adapter
and wrap the adapter in a security proxy. That often happens when
an adapter is turned over to untrusted code:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">IApp</span><span class="p">(</span><span class="n">Content</span><span class="p">(),</span> <span class="bp">None</span><span class="p">)</span> <span class="ow">is</span> <span class="bp">None</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.components.Comp"</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.components.IApp"</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent"</span>
<span class="gp">... </span><span class="s"> permission="zope.Public"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.security.checker</span> <span class="kn">import</span> <span class="n">ProxyFactory</span>
<span class="gp">>>> </span><span class="n">adapter</span> <span class="o">=</span> <span class="n">ProxyFactory</span><span class="p">(</span><span class="n">IApp</span><span class="p">(</span><span class="n">Content</span><span class="p">()))</span>
<span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.security.proxy</span> <span class="kn">import</span> <span class="n">getTestProxyItems</span>
<span class="gp">>>> </span><span class="n">items</span> <span class="o">=</span> <span class="p">[</span><span class="n">item</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="k">for</span> <span class="n">item</span> <span class="ow">in</span> <span class="n">getTestProxyItems</span><span class="p">(</span><span class="n">adapter</span><span class="p">)]</span>
<span class="gp">>>> </span><span class="n">items</span>
<span class="go">['a', 'f']</span>
<span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.security.proxy</span> <span class="kn">import</span> <span class="n">removeSecurityProxy</span>
<span class="gp">>>> </span><span class="n">removeSecurityProxy</span><span class="p">(</span><span class="n">adapter</span><span class="p">)</span><span class="o">.</span><span class="n">__class__</span> <span class="ow">is</span> <span class="n">Comp</span>
<span class="go">True</span>
</pre></div>
</div>
<p>Of course, this still works when we let the ZCML directive handler
figure out <tt class="docutils literal"><span class="pre">for</span></tt> and <tt class="docutils literal"><span class="pre">provides</span></tt> from the Python declarations:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.components.Comp"</span>
<span class="gp">... </span><span class="s"> permission="zope.Public"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">adapter</span> <span class="o">=</span> <span class="n">ProxyFactory</span><span class="p">(</span><span class="n">IApp</span><span class="p">(</span><span class="n">Content</span><span class="p">()))</span>
<span class="gp">>>> </span><span class="p">[</span><span class="n">item</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="k">for</span> <span class="n">item</span> <span class="ow">in</span> <span class="n">getTestProxyItems</span><span class="p">(</span><span class="n">adapter</span><span class="p">)]</span>
<span class="go">['a', 'f']</span>
<span class="gp">>>> </span><span class="n">removeSecurityProxy</span><span class="p">(</span><span class="n">adapter</span><span class="p">)</span><span class="o">.</span><span class="n">__class__</span> <span class="ow">is</span> <span class="n">Comp</span>
<span class="go">True</span>
</pre></div>
</div>
<p>It also works with multi adapters:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A3"</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.adapter.I3"</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent</span>
<span class="gp">... </span><span class="s"> zope.component.testfiles.adapter.I1</span>
<span class="gp">... </span><span class="s"> zope.component.testfiles.adapter.I2"</span>
<span class="gp">... </span><span class="s"> permission="zope.Public"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">content</span> <span class="o">=</span> <span class="n">Content</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">a1</span> <span class="o">=</span> <span class="n">A1</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">a2</span> <span class="o">=</span> <span class="n">A2</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">a3</span> <span class="o">=</span> <span class="n">ProxyFactory</span><span class="p">(</span><span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">queryMultiAdapter</span><span class="p">((</span><span class="n">content</span><span class="p">,</span> <span class="n">a1</span><span class="p">,</span> <span class="n">a2</span><span class="p">),</span> <span class="n">I3</span><span class="p">))</span>
<span class="gp">>>> </span><span class="n">a3</span><span class="o">.</span><span class="n">__class__</span> <span class="o">==</span> <span class="n">A3</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="p">[</span><span class="n">item</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="k">for</span> <span class="n">item</span> <span class="ow">in</span> <span class="n">getTestProxyItems</span><span class="p">(</span><span class="n">a3</span><span class="p">)]</span>
<span class="go">['f1', 'f2', 'f3']</span>
</pre></div>
</div>
<p>It’s probably not worth mentioning, but when we try to protect an
adapter with a permission that doesn’t exist, we’ll obviously get an
error:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.components.Comp"</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.components.IApp"</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent"</span>
<span class="gp">... </span><span class="s"> permission="zope.UndefinedPermission"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gt">Traceback (most recent call last):</span>
<span class="c">...</span>
<span class="gr">ConfigurationExecutionError: exceptions.ValueError</span>: <span class="n">('Undefined permission id', 'zope.UndefinedPermission')</span>
<span class="go"> in:</span>
<span class="go"> File "<string>", line 4.2-9.8</span>
<span class="go"> Could not read source.</span>
</pre></div>
</div>
</div>
<div class="section" id="trusted-adapters">
<h3>Trusted adapters<a class="headerlink" href="#trusted-adapters" title="Permalink to this headline">¶</a></h3>
<p>Trusted adapters are adapters that are trusted to do anything with the
objects they are given so that these objects are not security-proxied.
They are registered using the <tt class="docutils literal"><span class="pre">trusted</span></tt> argument to the <adapter />
directive:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent"</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.adapter.I1"</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A1"</span>
<span class="gp">... </span><span class="s"> trusted="yes"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
</pre></div>
</div>
<p>With an unproxied object, it’s business as usual:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">ob</span> <span class="o">=</span> <span class="n">Content</span><span class="p">()</span>
<span class="gp">>>> </span><span class="nb">type</span><span class="p">(</span><span class="n">I1</span><span class="p">(</span><span class="n">ob</span><span class="p">))</span> <span class="ow">is</span> <span class="n">A1</span>
<span class="go">True</span>
</pre></div>
</div>
<p>With a security-proxied object, however, we get a security-proxied
adapter:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">p</span> <span class="o">=</span> <span class="n">ProxyFactory</span><span class="p">(</span><span class="n">ob</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="n">I1</span><span class="p">(</span><span class="n">p</span><span class="p">)</span>
<span class="gp">>>> </span><span class="nb">type</span><span class="p">(</span><span class="n">a</span><span class="p">)</span>
<span class="go"><type 'zope.security._proxy._Proxy'></span>
</pre></div>
</div>
<p>While the adapter is security-proxied, the object it adapts is now
proxy-free. The adapter has umlimited access to it:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="n">removeSecurityProxy</span><span class="p">(</span><span class="n">a</span><span class="p">)</span>
<span class="gp">>>> </span><span class="nb">type</span><span class="p">(</span><span class="n">a</span><span class="p">)</span> <span class="ow">is</span> <span class="n">A1</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">a</span><span class="o">.</span><span class="n">context</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="ow">is</span> <span class="n">ob</span>
<span class="go">True</span>
</pre></div>
</div>
<p>We can also protect the trusted adapter with a permission:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">XMLConfig</span><span class="p">(</span><span class="s">'meta.zcml'</span><span class="p">,</span> <span class="n">zope</span><span class="o">.</span><span class="n">security</span><span class="p">)()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <permission</span>
<span class="gp">... </span><span class="s"> id="y.x"</span>
<span class="gp">... </span><span class="s"> title="XY"</span>
<span class="gp">... </span><span class="s"> description="Allow XY."</span>
<span class="gp">... </span><span class="s"> /></span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent"</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.adapter.I1"</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A1"</span>
<span class="gp">... </span><span class="s"> permission="y.x"</span>
<span class="gp">... </span><span class="s"> trusted="yes"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
</pre></div>
</div>
<p>Again, with an unproxied object, it’s business as usual:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">ob</span> <span class="o">=</span> <span class="n">Content</span><span class="p">()</span>
<span class="gp">>>> </span><span class="nb">type</span><span class="p">(</span><span class="n">I1</span><span class="p">(</span><span class="n">ob</span><span class="p">))</span> <span class="ow">is</span> <span class="n">A1</span>
<span class="go">True</span>
</pre></div>
</div>
<p>With a security-proxied object, we again get a security-proxied
adapter:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">p</span> <span class="o">=</span> <span class="n">ProxyFactory</span><span class="p">(</span><span class="n">ob</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="n">I1</span><span class="p">(</span><span class="n">p</span><span class="p">)</span>
<span class="gp">>>> </span><span class="nb">type</span><span class="p">(</span><span class="n">a</span><span class="p">)</span>
<span class="go"><type 'zope.security._proxy._Proxy'></span>
</pre></div>
</div>
<p>Since we protected the adapter with a permission, we now encounter a
location proxy behind the security proxy:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="n">removeSecurityProxy</span><span class="p">(</span><span class="n">a</span><span class="p">)</span>
<span class="gp">>>> </span><span class="nb">type</span><span class="p">(</span><span class="n">a</span><span class="p">)</span>
<span class="go"><class 'zope.location.location.LocationProxy'></span>
<span class="gp">>>> </span><span class="n">a</span><span class="o">.</span><span class="n">context</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="ow">is</span> <span class="n">ob</span>
<span class="go">True</span>
</pre></div>
</div>
<p>There’s one exception to all of this: When you use the public
permission (<tt class="docutils literal"><span class="pre">zope.Public</span></tt>), there will be no location proxy:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent"</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.adapter.I1"</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A1"</span>
<span class="gp">... </span><span class="s"> permission="zope.Public"</span>
<span class="gp">... </span><span class="s"> trusted="yes"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">ob</span> <span class="o">=</span> <span class="n">Content</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">p</span> <span class="o">=</span> <span class="n">ProxyFactory</span><span class="p">(</span><span class="n">ob</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="n">I1</span><span class="p">(</span><span class="n">p</span><span class="p">)</span>
<span class="gp">>>> </span><span class="nb">type</span><span class="p">(</span><span class="n">a</span><span class="p">)</span>
<span class="go"><type 'zope.security._proxy._Proxy'></span>
<span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="n">removeSecurityProxy</span><span class="p">(</span><span class="n">a</span><span class="p">)</span>
<span class="gp">>>> </span><span class="nb">type</span><span class="p">(</span><span class="n">a</span><span class="p">)</span> <span class="ow">is</span> <span class="n">A1</span>
<span class="go">True</span>
</pre></div>
</div>
<p>We can also explicitply pass the <tt class="docutils literal"><span class="pre">locate</span></tt> argument to make sure we
get location proxies:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <adapter</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent"</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.adapter.I1"</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A1"</span>
<span class="gp">... </span><span class="s"> trusted="yes"</span>
<span class="gp">... </span><span class="s"> locate="yes"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">ob</span> <span class="o">=</span> <span class="n">Content</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">p</span> <span class="o">=</span> <span class="n">ProxyFactory</span><span class="p">(</span><span class="n">ob</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="n">I1</span><span class="p">(</span><span class="n">p</span><span class="p">)</span>
<span class="gp">>>> </span><span class="nb">type</span><span class="p">(</span><span class="n">a</span><span class="p">)</span>
<span class="go"><type 'zope.security._proxy._Proxy'></span>
<span class="gp">>>> </span><span class="n">a</span> <span class="o">=</span> <span class="n">removeSecurityProxy</span><span class="p">(</span><span class="n">a</span><span class="p">)</span>
<span class="gp">>>> </span><span class="nb">type</span><span class="p">(</span><span class="n">a</span><span class="p">)</span>
<span class="go"><class 'zope.location.location.LocationProxy'></span>
</pre></div>
</div>
</div>
</div>
<div class="section" id="subscriber">
<h2>subscriber<a class="headerlink" href="#subscriber" title="Permalink to this headline">¶</a></h2>
<p>With the <subscriber /> directive you can register subscription
adapters or event subscribers with the adapter registry. Consider
this very typical example of a <subscriber /> directive:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <subscriber</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.adapter.IS"</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A3"</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent</span>
<span class="gp">... </span><span class="s"> zope.component.testfiles.adapter.I1"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">content</span> <span class="o">=</span> <span class="n">Content</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">a1</span> <span class="o">=</span> <span class="n">A1</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">subscribers</span> <span class="o">=</span> <span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">subscribers</span><span class="p">((</span><span class="n">content</span><span class="p">,</span> <span class="n">a1</span><span class="p">),</span> <span class="n">IS</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a3</span> <span class="o">=</span> <span class="n">subscribers</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
<span class="gp">>>> </span><span class="n">a3</span><span class="o">.</span><span class="n">__class__</span> <span class="ow">is</span> <span class="n">A3</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">a3</span><span class="o">.</span><span class="n">context</span> <span class="o">==</span> <span class="p">(</span><span class="n">content</span><span class="p">,</span> <span class="n">a1</span><span class="p">)</span>
<span class="go">True</span>
</pre></div>
</div>
<p>Note how ZCML provides some additional information when registering
components, such as the ZCML filename and line numbers:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">sm</span> <span class="o">=</span> <span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">getSiteManager</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">doc</span> <span class="o">=</span> <span class="p">[</span><span class="n">reg</span><span class="o">.</span><span class="n">info</span> <span class="k">for</span> <span class="n">reg</span> <span class="ow">in</span> <span class="n">sm</span><span class="o">.</span><span class="n">registeredSubscriptionAdapters</span><span class="p">()</span>
<span class="gp">... </span> <span class="k">if</span> <span class="n">reg</span><span class="o">.</span><span class="n">provided</span> <span class="ow">is</span> <span class="n">IS</span><span class="p">][</span><span class="mi">0</span><span class="p">]</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">doc</span>
<span class="go">File "<string>", line 4.2-9.8</span>
<span class="go"> Could not read source.</span>
</pre></div>
</div>
<p>The “fun” behind subscription adapters/subscribers is that when
several ones are declared for the same for/provides, they are all
found. With regular adapters, the most specific one (and in doubt the
one registered last) wins. Consider these two subscribers:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <subscriber</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.adapter.IS"</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A3"</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent</span>
<span class="gp">... </span><span class="s"> zope.component.testfiles.adapter.I1"</span>
<span class="gp">... </span><span class="s"> /></span>
<span class="gp">... </span><span class="s"> <subscriber</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.adapter.IS"</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A2"</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent</span>
<span class="gp">... </span><span class="s"> zope.component.testfiles.adapter.I1"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">subscribers</span> <span class="o">=</span> <span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">subscribers</span><span class="p">((</span><span class="n">content</span><span class="p">,</span> <span class="n">a1</span><span class="p">),</span> <span class="n">IS</span><span class="p">)</span>
<span class="gp">>>> </span><span class="nb">len</span><span class="p">(</span><span class="n">subscribers</span><span class="p">)</span>
<span class="go">2</span>
<span class="gp">>>> </span><span class="nb">sorted</span><span class="p">([</span><span class="n">a</span><span class="o">.</span><span class="n">__class__</span><span class="o">.</span><span class="n">__name__</span> <span class="k">for</span> <span class="n">a</span> <span class="ow">in</span> <span class="n">subscribers</span><span class="p">])</span>
<span class="go">['A2', 'A3']</span>
</pre></div>
</div>
<div class="section" id="id1">
<h3>Declaring <tt class="docutils literal"><span class="pre">for</span></tt> and <tt class="docutils literal"><span class="pre">provides</span></tt> in Python<a class="headerlink" href="#id1" title="Permalink to this headline">¶</a></h3>
<p>Like the <adapter /> directive, the <subscriber /> directive can
figure out from the in-line Python declaration (using
<tt class="docutils literal"><span class="pre">zope.component.adapts()</span></tt> or <tt class="docutils literal"><span class="pre">zope.component.adapter()</span></tt>) what the
subscriber should be registered for:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <subscriber</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.adapter.IS"</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A3"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">content</span> <span class="o">=</span> <span class="n">Content</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">a2</span> <span class="o">=</span> <span class="n">A2</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">subscribers</span> <span class="o">=</span> <span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">subscribers</span><span class="p">((</span><span class="n">content</span><span class="p">,</span> <span class="n">a1</span><span class="p">,</span> <span class="n">a2</span><span class="p">),</span> <span class="n">IS</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a3</span> <span class="o">=</span> <span class="n">subscribers</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
<span class="gp">>>> </span><span class="n">a3</span><span class="o">.</span><span class="n">__class__</span> <span class="ow">is</span> <span class="n">A3</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">a3</span><span class="o">.</span><span class="n">context</span> <span class="o">==</span> <span class="p">(</span><span class="n">content</span><span class="p">,</span> <span class="n">a1</span><span class="p">,</span> <span class="n">a2</span><span class="p">)</span>
<span class="go">True</span>
</pre></div>
</div>
<p>In the same way the directive can figure out what a subscriber
provides:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <subscriber handler="zope.component.testfiles.adapter.A3" />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">sm</span> <span class="o">=</span> <span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">getSiteManager</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">a3</span> <span class="o">=</span> <span class="n">sm</span><span class="o">.</span><span class="n">adapters</span><span class="o">.</span><span class="n">subscriptions</span><span class="p">((</span><span class="n">IContent</span><span class="p">,</span> <span class="n">I1</span><span class="p">,</span> <span class="n">I2</span><span class="p">),</span> <span class="bp">None</span><span class="p">)[</span><span class="mi">0</span><span class="p">]</span>
<span class="gp">>>> </span><span class="n">a3</span> <span class="ow">is</span> <span class="n">A3</span>
<span class="go">True</span>
</pre></div>
</div>
<p>A not so common edge case is declaring subscribers directly for
classes, not for interfaces. For example:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <subscriber</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.Content"</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.adapter.I1"</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A1"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">subs</span> <span class="o">=</span> <span class="nb">list</span><span class="p">(</span><span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">subscribers</span><span class="p">((</span><span class="n">Content</span><span class="p">(),),</span> <span class="n">I1</span><span class="p">))</span>
<span class="gp">>>> </span><span class="nb">isinstance</span><span class="p">(</span><span class="n">subs</span><span class="p">[</span><span class="mi">0</span><span class="p">],</span> <span class="n">A1</span><span class="p">)</span>
<span class="go">True</span>
</pre></div>
</div>
<p>This time, any object providing <tt class="docutils literal"><span class="pre">IContent</span></tt> won’t work if it’s not an
instance of the <tt class="docutils literal"><span class="pre">Content</span></tt> class:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">subscribers</span><span class="p">((</span><span class="n">MyContent</span><span class="p">(),),</span> <span class="n">I1</span><span class="p">))</span>
<span class="go">[]</span>
</pre></div>
</div>
</div>
<div class="section" id="protected-subscribers">
<h3>Protected subscribers<a class="headerlink" href="#protected-subscribers" title="Permalink to this headline">¶</a></h3>
<p>Subscribers can also be protected with a permission. First we have to
define a permission for which we’ll have to register the <permission />
directive:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">XMLConfig</span><span class="p">(</span><span class="s">'meta.zcml'</span><span class="p">,</span> <span class="n">zope</span><span class="o">.</span><span class="n">security</span><span class="p">)()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <permission</span>
<span class="gp">... </span><span class="s"> id="y.x"</span>
<span class="gp">... </span><span class="s"> title="XY"</span>
<span class="gp">... </span><span class="s"> description="Allow XY."</span>
<span class="gp">... </span><span class="s"> /></span>
<span class="gp">... </span><span class="s"> <subscriber</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.adapter.IS"</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A3"</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent</span>
<span class="gp">... </span><span class="s"> zope.component.testfiles.adapter.I1"</span>
<span class="gp">... </span><span class="s"> permission="y.x"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">subscribers</span> <span class="o">=</span> <span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">subscribers</span><span class="p">((</span><span class="n">content</span><span class="p">,</span> <span class="n">a1</span><span class="p">),</span> <span class="n">IS</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a3</span> <span class="o">=</span> <span class="n">subscribers</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
<span class="gp">>>> </span><span class="n">a3</span><span class="o">.</span><span class="n">__class__</span> <span class="ow">is</span> <span class="n">A3</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="nb">type</span><span class="p">(</span><span class="n">a3</span><span class="p">)</span>
<span class="go"><class 'zope.location.location.LocationProxy'></span>
<span class="gp">>>> </span><span class="n">a3</span><span class="o">.</span><span class="n">context</span> <span class="o">==</span> <span class="p">(</span><span class="n">content</span><span class="p">,</span> <span class="n">a1</span><span class="p">)</span>
<span class="go">True</span>
</pre></div>
</div>
</div>
<div class="section" id="trusted-subscribers">
<h3>Trusted subscribers<a class="headerlink" href="#trusted-subscribers" title="Permalink to this headline">¶</a></h3>
<p>Like trusted adapters, trusted subscribers are subscribers that are
trusted to do anything with the objects they are given so that these
objects are not security-proxied. In analogy to the <adapter />
directive, they are registered using the <tt class="docutils literal"><span class="pre">trusted</span></tt> argument to the
<subscriber /> directive:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <subscriber</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.adapter.IS"</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A3"</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent</span>
<span class="gp">... </span><span class="s"> zope.component.testfiles.adapter.I1"</span>
<span class="gp">... </span><span class="s"> trusted="yes"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
</pre></div>
</div>
<p>With an unproxied object, it’s business as usual:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">subscribers</span> <span class="o">=</span> <span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">subscribers</span><span class="p">((</span><span class="n">content</span><span class="p">,</span> <span class="n">a1</span><span class="p">),</span> <span class="n">IS</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a3</span> <span class="o">=</span> <span class="n">subscribers</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
<span class="gp">>>> </span><span class="n">a3</span><span class="o">.</span><span class="n">__class__</span> <span class="ow">is</span> <span class="n">A3</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">a3</span><span class="o">.</span><span class="n">context</span> <span class="o">==</span> <span class="p">(</span><span class="n">content</span><span class="p">,</span> <span class="n">a1</span><span class="p">)</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="nb">type</span><span class="p">(</span><span class="n">a3</span><span class="p">)</span> <span class="ow">is</span> <span class="n">A3</span>
<span class="go">True</span>
</pre></div>
</div>
<p>Now with a proxied object. We will see that the subscriber has
unproxied access to it, but the subscriber itself is proxied:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">p</span> <span class="o">=</span> <span class="n">ProxyFactory</span><span class="p">(</span><span class="n">content</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a3</span> <span class="o">=</span> <span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">subscribers</span><span class="p">((</span><span class="n">p</span><span class="p">,</span> <span class="n">a1</span><span class="p">),</span> <span class="n">IS</span><span class="p">)[</span><span class="mi">0</span><span class="p">]</span>
<span class="gp">>>> </span><span class="nb">type</span><span class="p">(</span><span class="n">a3</span><span class="p">)</span>
<span class="go"><type 'zope.security._proxy._Proxy'></span>
</pre></div>
</div>
<p>There’s no location proxy behind the security proxy:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">removeSecurityProxy</span><span class="p">(</span><span class="n">a3</span><span class="p">)</span><span class="o">.</span><span class="n">context</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="ow">is</span> <span class="n">content</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="nb">type</span><span class="p">(</span><span class="n">removeSecurityProxy</span><span class="p">(</span><span class="n">a3</span><span class="p">))</span> <span class="ow">is</span> <span class="n">A3</span>
<span class="go">True</span>
</pre></div>
</div>
<p>If you want the trusted subscriber to be located, you’ll also have to
use the <tt class="docutils literal"><span class="pre">locate</span></tt> argument:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <subscriber</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.adapter.IS"</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.adapter.A3"</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent</span>
<span class="gp">... </span><span class="s"> zope.component.testfiles.adapter.I1"</span>
<span class="gp">... </span><span class="s"> trusted="yes"</span>
<span class="gp">... </span><span class="s"> locate="yes"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
</pre></div>
</div>
<p>Again, it’s business as usual with an unproxied object:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">subscribers</span> <span class="o">=</span> <span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">subscribers</span><span class="p">((</span><span class="n">content</span><span class="p">,</span> <span class="n">a1</span><span class="p">),</span> <span class="n">IS</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a3</span> <span class="o">=</span> <span class="n">subscribers</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
<span class="gp">>>> </span><span class="n">a3</span><span class="o">.</span><span class="n">__class__</span> <span class="ow">is</span> <span class="n">A3</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">a3</span><span class="o">.</span><span class="n">context</span> <span class="o">==</span> <span class="p">(</span><span class="n">content</span><span class="p">,</span> <span class="n">a1</span><span class="p">)</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="nb">type</span><span class="p">(</span><span class="n">a3</span><span class="p">)</span> <span class="ow">is</span> <span class="n">A3</span>
<span class="go">True</span>
</pre></div>
</div>
<p>With a proxied object, we again get a security-proxied subscriber:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">p</span> <span class="o">=</span> <span class="n">ProxyFactory</span><span class="p">(</span><span class="n">content</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">a3</span> <span class="o">=</span> <span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">subscribers</span><span class="p">((</span><span class="n">p</span><span class="p">,</span> <span class="n">a1</span><span class="p">),</span> <span class="n">IS</span><span class="p">)[</span><span class="mi">0</span><span class="p">]</span>
<span class="gp">>>> </span><span class="nb">type</span><span class="p">(</span><span class="n">a3</span><span class="p">)</span>
<span class="go"><type 'zope.security._proxy._Proxy'></span>
<span class="gp">>>> </span><span class="n">removeSecurityProxy</span><span class="p">(</span><span class="n">a3</span><span class="p">)</span><span class="o">.</span><span class="n">context</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="ow">is</span> <span class="n">content</span>
<span class="go">True</span>
</pre></div>
</div>
<p>However, thanks to the <tt class="docutils literal"><span class="pre">locate</span></tt> argument, we now have a location
proxy behind the security proxy:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="nb">type</span><span class="p">(</span><span class="n">removeSecurityProxy</span><span class="p">(</span><span class="n">a3</span><span class="p">))</span>
<span class="go"><class 'zope.location.location.LocationProxy'></span>
</pre></div>
</div>
</div>
<div class="section" id="event-subscriber-handlers">
<h3>Event subscriber (handlers)<a class="headerlink" href="#event-subscriber-handlers" title="Permalink to this headline">¶</a></h3>
<p>Sometimes, subscribers don’t need to be adapters that actually provide
anything. It’s enough that a callable is called for a certain event.</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <subscriber</span>
<span class="gp">... </span><span class="s"> for="zope.component.testfiles.components.IContent</span>
<span class="gp">... </span><span class="s"> zope.component.testfiles.adapter.I1"</span>
<span class="gp">... </span><span class="s"> handler="zope.component.testfiles.adapter.Handler"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
</pre></div>
</div>
<p>In this case, simply getting the subscribers is enough to invoke them:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">subscribers</span><span class="p">((</span><span class="n">content</span><span class="p">,</span> <span class="n">a1</span><span class="p">),</span> <span class="bp">None</span><span class="p">))</span>
<span class="go">[]</span>
<span class="gp">>>> </span><span class="n">content</span><span class="o">.</span><span class="n">args</span> <span class="o">==</span> <span class="p">((</span><span class="n">a1</span><span class="p">,),)</span>
<span class="go">True</span>
</pre></div>
</div>
</div>
</div>
<div class="section" id="utility">
<h2>utility<a class="headerlink" href="#utility" title="Permalink to this headline">¶</a></h2>
<p>Apart from adapters (and subscription adapters), the Component
Architecture knows a second kind of component: utilities. They are
registered using the <utility /> directive.</p>
<p>Before we register the first test utility, we can verify that utility
lookup doesn’t work yet:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">queryUtility</span><span class="p">(</span><span class="n">IApp</span><span class="p">)</span> <span class="ow">is</span> <span class="bp">None</span>
<span class="go">True</span>
</pre></div>
</div>
<p>Then we register the utility:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <utility</span>
<span class="gp">... </span><span class="s"> component="zope.component.testfiles.components.comp"</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.components.IApp"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">getUtility</span><span class="p">(</span><span class="n">IApp</span><span class="p">)</span> <span class="ow">is</span> <span class="n">comp</span>
<span class="go">True</span>
</pre></div>
</div>
<p>Like adapters, utilities can also have names. There can be more than
one utility registered for a certain interface, as long as they each
have a different name.</p>
<p>First, we make sure that there’s no utility yet:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">queryUtility</span><span class="p">(</span><span class="n">IApp</span><span class="p">,</span> <span class="s">'test'</span><span class="p">)</span> <span class="ow">is</span> <span class="bp">None</span>
<span class="go">True</span>
</pre></div>
</div>
<p>Then we register it:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <utility</span>
<span class="gp">... </span><span class="s"> component="zope.component.testfiles.components.comp"</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.components.IApp"</span>
<span class="gp">... </span><span class="s"> name="test"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">getUtility</span><span class="p">(</span><span class="n">IApp</span><span class="p">,</span> <span class="s">'test'</span><span class="p">)</span> <span class="ow">is</span> <span class="n">comp</span>
<span class="go">True</span>
</pre></div>
</div>
<p>Utilities can also be registered from a factory. In this case, the
ZCML handler calls the factory (without any arguments) and registers
the returned value as a utility. Typically, you’d pass a class for
the factory:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">queryUtility</span><span class="p">(</span><span class="n">IApp</span><span class="p">)</span> <span class="ow">is</span> <span class="bp">None</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <utility</span>
<span class="gp">... </span><span class="s"> factory="zope.component.testfiles.components.Comp"</span>
<span class="gp">... </span><span class="s"> provides="zope.component.testfiles.components.IApp"</span>
<span class="gp">... </span><span class="s"> />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">getUtility</span><span class="p">(</span><span class="n">IApp</span><span class="p">)</span><span class="o">.</span><span class="n">__class__</span> <span class="ow">is</span> <span class="n">Comp</span>
<span class="go">True</span>
</pre></div>
</div>
<div class="section" id="declaring-provides-in-python">
<h3>Declaring <tt class="docutils literal"><span class="pre">provides</span></tt> in Python<a class="headerlink" href="#declaring-provides-in-python" title="Permalink to this headline">¶</a></h3>
<p>Like other directives, <utility /> can also figure out which interface
a utility provides from the Python declaration:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">queryUtility</span><span class="p">(</span><span class="n">IApp</span><span class="p">)</span> <span class="ow">is</span> <span class="bp">None</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <utility component="zope.component.testfiles.components.comp" />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">getUtility</span><span class="p">(</span><span class="n">IApp</span><span class="p">)</span> <span class="ow">is</span> <span class="n">comp</span>
<span class="go">True</span>
</pre></div>
</div>
<p>It won’t work if the component that is to be registered doesn’t
provide anything:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <utility component="zope.component.testfiles.adapter.a4" />'''</span><span class="p">)</span>
<span class="gt">Traceback (most recent call last):</span>
<span class="c">...</span>
<span class="gr">ZopeXMLConfigurationError</span>: <span class="n">File "<string>", line 4.2-4.61</span>
<span class="go"> TypeError: Missing 'provides' attribute</span>
</pre></div>
</div>
<p>Or if more than one interface is provided (then the ZCML directive
handler doesn’t know under which the utility should be registered):</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <utility component="zope.component.testfiles.adapter.a5" />'''</span><span class="p">)</span>
<span class="gt">Traceback (most recent call last):</span>
<span class="c">...</span>
<span class="gr">ZopeXMLConfigurationError</span>: <span class="n">File "<string>", line 4.2-4.61</span>
<span class="go"> TypeError: Missing 'provides' attribute</span>
</pre></div>
</div>
<p>We can repeat the same drill for utility factories:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <utility factory="zope.component.testfiles.components.Comp" />'''</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">getUtility</span><span class="p">(</span><span class="n">IApp</span><span class="p">)</span><span class="o">.</span><span class="n">__class__</span> <span class="ow">is</span> <span class="n">Comp</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <utility factory="zope.component.testfiles.adapter.A4" />'''</span><span class="p">)</span>
<span class="gt">Traceback (most recent call last):</span>
<span class="c">...</span>
<span class="gr">ZopeXMLConfigurationError</span>: <span class="n">File "<string>", line 4.2-4.59</span>
<span class="go"> TypeError: Missing 'provides' attribute</span>
<span class="gp">>>> </span><span class="n">clearZCML</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">runSnippet</span><span class="p">(</span><span class="s">'''</span>
<span class="gp">... </span><span class="s"> <utility factory="zope.component.testfiles.adapter.A5" />'''</span><span class="p">)</span>
<span class="gt">Traceback (most recent call last):</span>
<span class="c">...</span>
<span class="gr">ZopeXMLConfigurationError</span>: <span class="n">File "<string>", line 4.2-4.59</span>
<span class="go"> TypeError: Missing 'provides' attribute</span>
</pre></div>
</div>
</div>
<div class="section" id="protected-utilities">
<h3>Protected utilities<a class="headerlink" href="#protected-utilities" title="Permalink to this headline">¶</a></h3>
<p>TODO:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="k">def</span> <span class="nf">testProtectedUtility</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="sd">"""Test that we can protect a utility.</span>
<span class="sd"> Also:</span>
<span class="sd"> Check that multiple configurations for the same utility and</span>
<span class="sd"> don't interfere.</span>
<span class="sd"> """</span>
<span class="bp">self</span><span class="o">.</span><span class="n">assertEqual</span><span class="p">(</span><span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">queryUtility</span><span class="p">(</span><span class="n">IV</span><span class="p">),</span> <span class="bp">None</span><span class="p">)</span>
<span class="n">xmlconfig</span><span class="p">(</span><span class="n">StringIO</span><span class="p">(</span><span class="n">template</span> <span class="o">%</span> <span class="p">(</span>
<span class="sd">'''</span>
<span class="sd"> <permission id="tell.everyone" title="Yay" /></span>
<span class="sd"> <utility</span>
<span class="sd"> component="zope.component.testfiles.components.comp"</span>
<span class="sd"> provides="zope.component.testfiles.components.IApp"</span>
<span class="sd"> permission="tell.everyone"</span>
<span class="sd"> /></span>
<span class="sd"> <permission id="top.secret" title="shhhh" /></span>
<span class="sd"> <utility</span>
<span class="sd"> component="zope.component.testfiles.components.comp"</span>
<span class="sd"> provides="zope.component.testfiles.components.IAppb"</span>
<span class="sd"> permission="top.secret"</span>
<span class="sd"> /></span>
<span class="sd"> '''</span>
<span class="p">)))</span>
<span class="n">utility</span> <span class="o">=</span> <span class="n">ProxyFactory</span><span class="p">(</span><span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">getUtility</span><span class="p">(</span><span class="n">IApp</span><span class="p">))</span>
<span class="n">items</span> <span class="o">=</span> <span class="n">getTestProxyItems</span><span class="p">(</span><span class="n">utility</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">assertEqual</span><span class="p">(</span><span class="n">items</span><span class="p">,</span> <span class="p">[(</span><span class="s">'a'</span><span class="p">,</span> <span class="s">'tell.everyone'</span><span class="p">),</span>
<span class="p">(</span><span class="s">'f'</span><span class="p">,</span> <span class="s">'tell.everyone'</span><span class="p">)</span>
<span class="p">])</span>
<span class="bp">self</span><span class="o">.</span><span class="n">assertEqual</span><span class="p">(</span><span class="n">removeSecurityProxy</span><span class="p">(</span><span class="n">utility</span><span class="p">),</span> <span class="n">comp</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">testUtilityUndefinedPermission</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="n">config</span> <span class="o">=</span> <span class="n">StringIO</span><span class="p">(</span><span class="n">template</span> <span class="o">%</span> <span class="p">(</span>
<span class="sd">'''</span>
<span class="sd"> <utility</span>
<span class="sd"> component="zope.component.testfiles.components.comp"</span>
<span class="sd"> provides="zope.component.testfiles.components.IApp"</span>
<span class="sd"> permission="zope.UndefinedPermission"</span>
<span class="sd"> /></span>
<span class="sd"> '''</span>
<span class="p">))</span>
<span class="bp">self</span><span class="o">.</span><span class="n">assertRaises</span><span class="p">(</span><span class="ne">ValueError</span><span class="p">,</span> <span class="n">xmlconfig</span><span class="p">,</span> <span class="n">config</span><span class="p">,</span>
<span class="n">testing</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span>
</pre></div>
</div>
</div>
</div>
<div class="section" id="interface">
<h2>interface<a class="headerlink" href="#interface" title="Permalink to this headline">¶</a></h2>
<p>The <interface /> directive lets us register an interface. Interfaces
are registered as named utilities. We therefore needn’t go though all
the lookup details again, it is sufficient to see whether the
directive handler emits the right actions.</p>
<p>First we provide a stub configuration context:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">re</span><span class="o">,</span> <span class="nn">pprint</span>
<span class="gp">>>> </span><span class="n">atre</span> <span class="o">=</span> <span class="n">re</span><span class="o">.</span><span class="n">compile</span><span class="p">(</span><span class="s">' at [0-9a-fA-Fx]+'</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">class</span> <span class="nc">Context</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="gp">... </span> <span class="n">actions</span> <span class="o">=</span> <span class="p">()</span>
<span class="gp">... </span> <span class="k">def</span> <span class="nf">action</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">discriminator</span><span class="p">,</span> <span class="nb">callable</span><span class="p">,</span> <span class="n">args</span><span class="p">):</span>
<span class="gp">... </span> <span class="bp">self</span><span class="o">.</span><span class="n">actions</span> <span class="o">+=</span> <span class="p">((</span><span class="n">discriminator</span><span class="p">,</span> <span class="nb">callable</span><span class="p">,</span> <span class="n">args</span><span class="p">),</span> <span class="p">)</span>
<span class="gp">... </span> <span class="k">def</span> <span class="nf">__repr__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="gp">... </span> <span class="n">stream</span> <span class="o">=</span> <span class="n">StringIO</span><span class="p">()</span>
<span class="gp">... </span> <span class="n">pprinter</span> <span class="o">=</span> <span class="n">pprint</span><span class="o">.</span><span class="n">PrettyPrinter</span><span class="p">(</span><span class="n">stream</span><span class="o">=</span><span class="n">stream</span><span class="p">,</span> <span class="n">width</span><span class="o">=</span><span class="mi">60</span><span class="p">)</span>
<span class="gp">... </span> <span class="n">pprinter</span><span class="o">.</span><span class="n">pprint</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">actions</span><span class="p">)</span>
<span class="gp">... </span> <span class="n">r</span> <span class="o">=</span> <span class="n">stream</span><span class="o">.</span><span class="n">getvalue</span><span class="p">()</span>
<span class="gp">... </span> <span class="k">return</span> <span class="p">(</span><span class="s">''</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">atre</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="n">r</span><span class="p">)))</span><span class="o">.</span><span class="n">strip</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">context</span> <span class="o">=</span> <span class="n">Context</span><span class="p">()</span>
</pre></div>
</div>
<p>Then we provide a test interface that we’d like to register:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.interface</span> <span class="kn">import</span> <span class="n">Interface</span>
<span class="gp">>>> </span><span class="k">class</span> <span class="nc">I</span><span class="p">(</span><span class="n">Interface</span><span class="p">):</span>
<span class="gp">... </span> <span class="k">pass</span>
</pre></div>
</div>
<p>It doesn’t yet provide <tt class="docutils literal"><span class="pre">ITestType</span></tt>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.component.tests.examples</span> <span class="kn">import</span> <span class="n">ITestType</span>
<span class="gp">>>> </span><span class="n">ITestType</span><span class="o">.</span><span class="n">providedBy</span><span class="p">(</span><span class="n">I</span><span class="p">)</span>
<span class="go">False</span>
</pre></div>
</div>
<p>However, after calling the directive handler...</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.component.zcml</span> <span class="kn">import</span> <span class="n">interface</span>
<span class="gp">>>> </span><span class="n">interface</span><span class="p">(</span><span class="n">context</span><span class="p">,</span> <span class="n">I</span><span class="p">,</span> <span class="n">ITestType</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">context</span>
<span class="go">((None,</span>
<span class="go"> <function provideInterface>,</span>
<span class="go"> ('',</span>
<span class="go"> <InterfaceClass __builtin__.I>,</span>
<span class="go"> <InterfaceClass zope.component.tests.examples.ITestType>)),)</span>
</pre></div>
</div>
<p>...it does provide <tt class="docutils literal"><span class="pre">ITestType</span></tt>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.interface.interfaces</span> <span class="kn">import</span> <span class="n">IInterface</span>
<span class="gp">>>> </span><span class="n">ITestType</span><span class="o">.</span><span class="n">extends</span><span class="p">(</span><span class="n">IInterface</span><span class="p">)</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">IInterface</span><span class="o">.</span><span class="n">providedBy</span><span class="p">(</span><span class="n">I</span><span class="p">)</span>
<span class="go">True</span>
</pre></div>
</div>
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<h3><a href="index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">ZCML directives</a><ul>
<li><a class="reference internal" href="#adapter">adapter</a><ul>
<li><a class="reference internal" href="#adapter-factories">Adapter factories</a></li>
<li><a class="reference internal" href="#declaring-for-and-provides-in-python">Declaring <tt class="docutils literal"><span class="pre">for</span></tt> and <tt class="docutils literal"><span class="pre">provides</span></tt> in Python</a></li>
<li><a class="reference internal" href="#multi-adapters">Multi-adapters</a></li>
<li><a class="reference internal" href="#protected-adapters">Protected adapters</a></li>
<li><a class="reference internal" href="#trusted-adapters">Trusted adapters</a></li>
</ul>
</li>
<li><a class="reference internal" href="#subscriber">subscriber</a><ul>
<li><a class="reference internal" href="#id1">Declaring <tt class="docutils literal"><span class="pre">for</span></tt> and <tt class="docutils literal"><span class="pre">provides</span></tt> in Python</a></li>
<li><a class="reference internal" href="#protected-subscribers">Protected subscribers</a></li>
<li><a class="reference internal" href="#trusted-subscribers">Trusted subscribers</a></li>
<li><a class="reference internal" href="#event-subscriber-handlers">Event subscriber (handlers)</a></li>
</ul>
</li>
<li><a class="reference internal" href="#utility">utility</a><ul>
<li><a class="reference internal" href="#declaring-provides-in-python">Declaring <tt class="docutils literal"><span class="pre">provides</span></tt> in Python</a></li>
<li><a class="reference internal" href="#protected-utilities">Protected utilities</a></li>
</ul>
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<li><a class="reference internal" href="#interface">interface</a></li>
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