EVOLUTION-MANAGER

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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>
Components may be registered using the registration API exposed by
<tt class="docutils literal">zope.component</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.
In ZCML, each XML element is a directive. There are different
top-level directives that let us register components. We will
introduce them one by one here.
This helper will let us easily execute ZCML snippets:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; from cStringIO import StringIO
&gt;&gt;&gt; from zope.configuration.xmlconfig import xmlconfig
&gt;&gt;&gt; def runSnippet(snippet):
... template = &quot;&quot;&quot;\
... &lt;configure xmlns=&#39;http://namespaces.zope.org/zope&#39;
... i18n_domain=&quot;zope&quot;&gt;
... %s
... &lt;/configure&gt;&quot;&quot;&quot;
... xmlconfig(StringIO(template % snippet))
</pre></div>
</div>
<div class="section" id="adapter">
<h2>adapter<a class="headerlink" href="#adapter" title="Permalink to this headline">¶</a></h2>
Adapters play a key role in the Component Architecture. In ZCML, they
are registered with the &lt;adapter /&gt; directive.
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; from zope.component.testfiles.adapter import A1, A2, A3, Handler
&gt;&gt;&gt; from zope.component.testfiles.adapter import I1, I2, I3, IS
&gt;&gt;&gt; from zope.component.testfiles.components import IContent, Content, Comp, comp
</pre></div>
</div>
Before we register the first test adapter, we can verify that adapter
lookup doesn&#8217;t work yet:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; from zope.component.tests.examples import clearZCML
&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; from zope.component.testfiles.components import IApp
&gt;&gt;&gt; IApp(Content(), None) is None
True
</pre></div>
</div>
Then we register the adapter and see that the lookup works:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;adapter
... factory=&quot;zope.component.testfiles.components.Comp&quot;
... provides=&quot;zope.component.testfiles.components.IApp&quot;
... for=&quot;zope.component.testfiles.components.IContent&quot;
... /&gt;&#39;&#39;&#39;)

&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;adapter
... factory=&quot;zope.component.testfiles.components.Comp&quot;
... provides=&quot;zope.component.testfiles.components.IApp&quot;
... for=&quot;zope.component.testfiles.components.IContent&quot;
... name=&quot;test&quot;
... /&gt;&#39;&#39;&#39;)

&gt;&gt;&gt; zope.component.getAdapter(Content(), IApp, &#39;test&#39;).__class__
&lt;class &#39;zope.component.testfiles.components.Comp&#39;&gt;
</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>
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:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;adapter
... factory=&quot;zope.component.testfiles.adapter.A1
... zope.component.testfiles.adapter.A2
... zope.component.testfiles.adapter.A3&quot;
... provides=&quot;zope.component.testfiles.components.IApp&quot;
... for=&quot;zope.component.testfiles.components.IContent&quot;
... /&gt;&#39;&#39;&#39;)
</pre></div>
</div>
The resulting adapter is an A3, around an A2, around an A1, around the
adapted object:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; content = Content()
&gt;&gt;&gt; a3 = IApp(content)
&gt;&gt;&gt; a3.__class__ is A3
True

&gt;&gt;&gt; a2 = a3.context[0]
&gt;&gt;&gt; a2.__class__ is A2
True

&gt;&gt;&gt; a1 = a2.context[0]
&gt;&gt;&gt; a1.__class__ is A1
True

&gt;&gt;&gt; a1.context[0] is content
True
</pre></div>
</div>
Of course, if no factory is provided at all, we will get an error:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;adapter
... factory=&quot;&quot;
... provides=&quot;zope.component.testfiles.components.IApp&quot;
... for=&quot;zope.component.testfiles.components.IContent&quot;
... /&gt;&#39;&#39;&#39;)
Traceback (most recent call last):
 ...
ZopeXMLConfigurationError: File &quot;&lt;string&gt;&quot;, line 4.2-8.8
 ValueError: No factory specified
</pre></div>
</div>
</div>
<div class="section" id="declaring-for-and-provides-in-python">
<h3>Declaring <tt class="docutils literal">for</tt> and <tt class="docutils literal">provides</tt> in Python<a class="headerlink" href="#declaring-for-and-provides-in-python" title="Permalink to this headline">¶</a></h3>
The &lt;adapter /&gt; directive can figure out from the in-line Python
declaration (using <tt class="docutils literal">zope.component.adapts()</tt> or
<tt class="docutils literal">zope.component.adapter()</tt> as well as <tt class="docutils literal">zope.interface.implements</tt>)
what the adapter should be registered for and what it provides:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; IApp(Content(), None) is None
True

&gt;&gt;&gt; IApp(Content()).__class__
&lt;class &#39;zope.component.testfiles.components.Comp&#39;&gt;
</pre></div>
</div>
Of course, if the adapter has no <tt class="docutils literal">implements()</tt> declaration, ZCML
can&#8217;t figure out what it provides:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;adapter
... factory=&quot;zope.component.testfiles.adapter.A4&quot;
... for=&quot;zope.component.testfiles.components.IContent&quot;
... /&gt;&#39;&#39;&#39;)
Traceback (most recent call last):
 ...
ZopeXMLConfigurationError: File &quot;&lt;string&gt;&quot;, line 4.2-7.8
 TypeError: Missing &#39;provides&#39; attribute
</pre></div>
</div>
On the other hand, if the factory implements more than one interface,
ZCML can&#8217;t figure out what it should provide either:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;adapter
... factory=&quot;zope.component.testfiles.adapter.A5&quot;
... for=&quot;zope.component.testfiles.components.IContent&quot;
... /&gt;&#39;&#39;&#39;)
Traceback (most recent call last):
 ...
ZopeXMLConfigurationError: File &quot;&lt;string&gt;&quot;, line 4.2-7.8
 TypeError: Missing &#39;provides&#39; attribute
</pre></div>
</div>
A not so common edge case is registering adapters directly for
classes, not for interfaces. For example:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;adapter
... for=&quot;zope.component.testfiles.components.Content&quot;
... provides=&quot;zope.component.testfiles.adapter.I1&quot;
... factory=&quot;zope.component.testfiles.adapter.A1&quot;
... /&gt;&#39;&#39;&#39;)

&gt;&gt;&gt; a3 = zope.component.queryMultiAdapter((content, a1, a2), I3)
&gt;&gt;&gt; a3.__class__ is A3
True
&gt;&gt;&gt; a3.context == (content, a1, a2)
True
</pre></div>
</div>
Chained factories are not supported for multi-adapters, though:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;adapter
... for=&quot;zope.component.testfiles.components.IContent
... zope.component.testfiles.adapter.I1
... zope.component.testfiles.adapter.I2&quot;
... provides=&quot;zope.component.testfiles.components.IApp&quot;
... factory=&quot;zope.component.testfiles.adapter.A1
... zope.component.testfiles.adapter.A2&quot;
... /&gt;&#39;&#39;&#39;)
Traceback (most recent call last):
 ...
ZopeXMLConfigurationError: File &quot;&lt;string&gt;&quot;, line 4.2-11.8
 ValueError: Can&#39;t use multiple factories and multiple for
</pre></div>
</div>
And neither for null-adapters:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;adapter
... for=&quot;&quot;
... provides=&quot;zope.component.testfiles.components.IApp&quot;
... factory=&quot;zope.component.testfiles.adapter.A1
... zope.component.testfiles.adapter.A2&quot;
... /&gt;&#39;&#39;&#39;)
Traceback (most recent call last):
 ...
ZopeXMLConfigurationError: File &quot;&lt;string&gt;&quot;, line 4.2-9.8
 ValueError: Can&#39;t use multiple factories and multiple for
</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>
Adapters can be protected with a permission. First we have to define
a permission for which we&#8217;ll have to register the &lt;permission /&gt;
directive:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; IApp(Content(), None) is None
True

&gt;&gt;&gt; import zope.security
&gt;&gt;&gt; from zope.configuration.xmlconfig import XMLConfig
&gt;&gt;&gt; XMLConfig(&#39;meta.zcml&#39;, zope.security)()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;permission
... id=&quot;y.x&quot;
... title=&quot;XY&quot;
... description=&quot;Allow XY.&quot;
... /&gt;
... &lt;adapter
... factory=&quot;zope.component.testfiles.components.Comp&quot;
... provides=&quot;zope.component.testfiles.components.IApp&quot;
... for=&quot;zope.component.testfiles.components.IContent&quot;
... permission=&quot;y.x&quot;
... /&gt;&#39;&#39;&#39;)
</pre></div>
</div>
We see that the adapter is a location proxy now so that the
appropriate permissions can be found from the context:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; IApp(Content()).__class__
&lt;class &#39;zope.component.testfiles.components.Comp&#39;&gt;
&gt;&gt;&gt; type(IApp(Content()))
&lt;class &#39;zope.location.location.LocationProxy&#39;&gt;
</pre></div>
</div>
We can also go about it a different way. Let&#8217;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:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; IApp(Content(), None) is None
True

&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;adapter
... factory=&quot;zope.component.testfiles.components.Comp&quot;
... provides=&quot;zope.component.testfiles.components.IApp&quot;
... for=&quot;zope.component.testfiles.components.IContent&quot;
... permission=&quot;zope.Public&quot;
... /&gt;&#39;&#39;&#39;)

&gt;&gt;&gt; from zope.security.checker import ProxyFactory
&gt;&gt;&gt; adapter = ProxyFactory(IApp(Content()))
&gt;&gt;&gt; from zope.security.proxy import getTestProxyItems
&gt;&gt;&gt; items = [item[0] for item in getTestProxyItems(adapter)]
&gt;&gt;&gt; items
[&#39;a&#39;, &#39;f&#39;]

&gt;&gt;&gt; from zope.security.proxy import removeSecurityProxy
&gt;&gt;&gt; removeSecurityProxy(adapter).__class__ is Comp
True
</pre></div>
</div>
Of course, this still works when we let the ZCML directive handler
figure out <tt class="docutils literal">for</tt> and <tt class="docutils literal">provides</tt> from the Python declarations:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;adapter
... factory=&quot;zope.component.testfiles.components.Comp&quot;
... permission=&quot;zope.Public&quot;
... /&gt;&#39;&#39;&#39;)

&gt;&gt;&gt; adapter = ProxyFactory(IApp(Content()))
&gt;&gt;&gt; [item[0] for item in getTestProxyItems(adapter)]
[&#39;a&#39;, &#39;f&#39;]
&gt;&gt;&gt; removeSecurityProxy(adapter).__class__ is Comp
True
</pre></div>
</div>
It also works with multi adapters:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;adapter
... factory=&quot;zope.component.testfiles.adapter.A3&quot;
... provides=&quot;zope.component.testfiles.adapter.I3&quot;
... for=&quot;zope.component.testfiles.components.IContent
... zope.component.testfiles.adapter.I1
... zope.component.testfiles.adapter.I2&quot;
... permission=&quot;zope.Public&quot;
... /&gt;&#39;&#39;&#39;)

&gt;&gt;&gt; content = Content()
&gt;&gt;&gt; a1 = A1()
&gt;&gt;&gt; a2 = A2()
&gt;&gt;&gt; a3 = ProxyFactory(zope.component.queryMultiAdapter((content, a1, a2), I3))
&gt;&gt;&gt; a3.__class__ == A3
True
&gt;&gt;&gt; [item[0] for item in getTestProxyItems(a3)]
[&#39;f1&#39;, &#39;f2&#39;, &#39;f3&#39;]
</pre></div>
</div>
It&#8217;s probably not worth mentioning, but when we try to protect an
adapter with a permission that doesn&#8217;t exist, we&#8217;ll obviously get an
error:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;adapter
... factory=&quot;zope.component.testfiles.components.Comp&quot;
... provides=&quot;zope.component.testfiles.components.IApp&quot;
... for=&quot;zope.component.testfiles.components.IContent&quot;
... permission=&quot;zope.UndefinedPermission&quot;
... /&gt;&#39;&#39;&#39;)
Traceback (most recent call last):
 ...
ConfigurationExecutionError: exceptions.ValueError: (&#39;Undefined permission id&#39;, &#39;zope.UndefinedPermission&#39;)
 in:
 File &quot;&lt;string&gt;&quot;, line 4.2-9.8
 Could not read source.
</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>
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">trusted</tt> argument to the &lt;adapter /&gt;
directive:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;adapter
... for=&quot;zope.component.testfiles.components.IContent&quot;
... provides=&quot;zope.component.testfiles.adapter.I1&quot;
... factory=&quot;zope.component.testfiles.adapter.A1&quot;
... trusted=&quot;yes&quot;
... /&gt;&#39;&#39;&#39;)
</pre></div>
</div>
With an unproxied object, it&#8217;s business as usual:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; ob = Content()
&gt;&gt;&gt; type(I1(ob)) is A1
True
</pre></div>
</div>
With a security-proxied object, however, we get a security-proxied
adapter:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; p = ProxyFactory(ob)
&gt;&gt;&gt; a = I1(p)
&gt;&gt;&gt; type(a)
&lt;type &#39;zope.security._proxy._Proxy&#39;&gt;
</pre></div>
</div>
While the adapter is security-proxied, the object it adapts is now
proxy-free. The adapter has umlimited access to it:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; a = removeSecurityProxy(a)
&gt;&gt;&gt; type(a) is A1
True
&gt;&gt;&gt; a.context[0] is ob
True
</pre></div>
</div>
We can also protect the trusted adapter with a permission:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; XMLConfig(&#39;meta.zcml&#39;, zope.security)()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;permission
... id=&quot;y.x&quot;
... title=&quot;XY&quot;
... description=&quot;Allow XY.&quot;
... /&gt;
... &lt;adapter
... for=&quot;zope.component.testfiles.components.IContent&quot;
... provides=&quot;zope.component.testfiles.adapter.I1&quot;
... factory=&quot;zope.component.testfiles.adapter.A1&quot;
... permission=&quot;y.x&quot;
... trusted=&quot;yes&quot;
... /&gt;&#39;&#39;&#39;)
</pre></div>
</div>
Again, with an unproxied object, it&#8217;s business as usual:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; ob = Content()
&gt;&gt;&gt; type(I1(ob)) is A1
True
</pre></div>
</div>
With a security-proxied object, we again get a security-proxied
adapter:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; p = ProxyFactory(ob)
&gt;&gt;&gt; a = I1(p)
&gt;&gt;&gt; type(a)
&lt;type &#39;zope.security._proxy._Proxy&#39;&gt;
</pre></div>
</div>
Since we protected the adapter with a permission, we now encounter a
location proxy behind the security proxy:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; a = removeSecurityProxy(a)
&gt;&gt;&gt; type(a)
&lt;class &#39;zope.location.location.LocationProxy&#39;&gt;
&gt;&gt;&gt; a.context[0] is ob
True
</pre></div>
</div>
There&#8217;s one exception to all of this: When you use the public
permission (<tt class="docutils literal">zope.Public</tt>), there will be no location proxy:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;adapter
... for=&quot;zope.component.testfiles.components.IContent&quot;
... provides=&quot;zope.component.testfiles.adapter.I1&quot;
... factory=&quot;zope.component.testfiles.adapter.A1&quot;
... permission=&quot;zope.Public&quot;
... trusted=&quot;yes&quot;
... /&gt;&#39;&#39;&#39;)

&gt;&gt;&gt; ob = Content()
&gt;&gt;&gt; p = ProxyFactory(ob)
&gt;&gt;&gt; a = I1(p)
&gt;&gt;&gt; type(a)
&lt;type &#39;zope.security._proxy._Proxy&#39;&gt;

&gt;&gt;&gt; a = removeSecurityProxy(a)
&gt;&gt;&gt; type(a) is A1
True
</pre></div>
</div>
We can also explicitply pass the <tt class="docutils literal">locate</tt> argument to make sure we
get location proxies:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;adapter
... for=&quot;zope.component.testfiles.components.IContent&quot;
... provides=&quot;zope.component.testfiles.adapter.I1&quot;
... factory=&quot;zope.component.testfiles.adapter.A1&quot;
... trusted=&quot;yes&quot;
... locate=&quot;yes&quot;
... /&gt;&#39;&#39;&#39;)

&gt;&gt;&gt; a = removeSecurityProxy(a)
&gt;&gt;&gt; type(a)
&lt;class &#39;zope.location.location.LocationProxy&#39;&gt;
</pre></div>
</div>
</div>
</div>
<div class="section" id="subscriber">
<h2>subscriber<a class="headerlink" href="#subscriber" title="Permalink to this headline">¶</a></h2>
With the &lt;subscriber /&gt; directive you can register subscription
adapters or event subscribers with the adapter registry. Consider
this very typical example of a &lt;subscriber /&gt; directive:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;subscriber
... provides=&quot;zope.component.testfiles.adapter.IS&quot;
... factory=&quot;zope.component.testfiles.adapter.A3&quot;
... for=&quot;zope.component.testfiles.components.IContent
... zope.component.testfiles.adapter.I1&quot;
... /&gt;&#39;&#39;&#39;)

&gt;&gt;&gt; a3 = subscribers[0]
&gt;&gt;&gt; a3.__class__ is A3
True
&gt;&gt;&gt; a3.context == (content, a1, a2)
True
</pre></div>
</div>
In the same way the directive can figure out what a subscriber
provides:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;subscriber handler=&quot;zope.component.testfiles.adapter.A3&quot; /&gt;&#39;&#39;&#39;)

&gt;&gt;&gt; sm = zope.component.getSiteManager()
&gt;&gt;&gt; a3 = sm.adapters.subscriptions((IContent, I1, I2), None)[0]
&gt;&gt;&gt; a3 is A3
True
</pre></div>
</div>
A not so common edge case is declaring subscribers directly for
classes, not for interfaces. For example:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;subscriber
... for=&quot;zope.component.testfiles.components.Content&quot;
... provides=&quot;zope.component.testfiles.adapter.I1&quot;
... factory=&quot;zope.component.testfiles.adapter.A1&quot;
... /&gt;&#39;&#39;&#39;)

&gt;&gt;&gt; subs = list(zope.component.subscribers((Content(),), I1))
&gt;&gt;&gt; isinstance(subs[0], A1)
True
</pre></div>
</div>
This time, any object providing <tt class="docutils literal">IContent</tt> won&#8217;t work if it&#8217;s not an
instance of the <tt class="docutils literal">Content</tt> class:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; list(zope.component.subscribers((MyContent(),), I1))
[]
</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>
Subscribers can also be protected with a permission. First we have to
define a permission for which we&#8217;ll have to register the &lt;permission /&gt;
directive:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; XMLConfig(&#39;meta.zcml&#39;, zope.security)()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;permission
... id=&quot;y.x&quot;
... title=&quot;XY&quot;
... description=&quot;Allow XY.&quot;
... /&gt;
... &lt;subscriber
... provides=&quot;zope.component.testfiles.adapter.IS&quot;
... factory=&quot;zope.component.testfiles.adapter.A3&quot;
... for=&quot;zope.component.testfiles.components.IContent
... zope.component.testfiles.adapter.I1&quot;
... permission=&quot;y.x&quot;
... /&gt;&#39;&#39;&#39;)

&gt;&gt;&gt; subscribers = zope.component.subscribers((content, a1), IS)
&gt;&gt;&gt; a3 = subscribers[0]
&gt;&gt;&gt; a3.__class__ is A3
True
&gt;&gt;&gt; type(a3)
&lt;class &#39;zope.location.location.LocationProxy&#39;&gt;
&gt;&gt;&gt; a3.context == (content, a1)
True
</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>
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 &lt;adapter /&gt;
directive, they are registered using the <tt class="docutils literal">trusted</tt> argument to the
&lt;subscriber /&gt; directive:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;subscriber
... provides=&quot;zope.component.testfiles.adapter.IS&quot;
... factory=&quot;zope.component.testfiles.adapter.A3&quot;
... for=&quot;zope.component.testfiles.components.IContent
... zope.component.testfiles.adapter.I1&quot;
... trusted=&quot;yes&quot;
... /&gt;&#39;&#39;&#39;)
</pre></div>
</div>
With an unproxied object, it&#8217;s business as usual:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; subscribers = zope.component.subscribers((content, a1), IS)
&gt;&gt;&gt; a3 = subscribers[0]
&gt;&gt;&gt; a3.__class__ is A3
True
&gt;&gt;&gt; a3.context == (content, a1)
True
&gt;&gt;&gt; type(a3) is A3
True
</pre></div>
</div>
Now with a proxied object. We will see that the subscriber has
unproxied access to it, but the subscriber itself is proxied:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; p = ProxyFactory(content)
&gt;&gt;&gt; a3 = zope.component.subscribers((p, a1), IS)[0]
&gt;&gt;&gt; type(a3)
&lt;type &#39;zope.security._proxy._Proxy&#39;&gt;
</pre></div>
</div>
There&#8217;s no location proxy behind the security proxy:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; removeSecurityProxy(a3).context[0] is content
True
&gt;&gt;&gt; type(removeSecurityProxy(a3)) is A3
True
</pre></div>
</div>
If you want the trusted subscriber to be located, you&#8217;ll also have to
use the <tt class="docutils literal">locate</tt> argument:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;subscriber
... provides=&quot;zope.component.testfiles.adapter.IS&quot;
... factory=&quot;zope.component.testfiles.adapter.A3&quot;
... for=&quot;zope.component.testfiles.components.IContent
... zope.component.testfiles.adapter.I1&quot;
... trusted=&quot;yes&quot;
... locate=&quot;yes&quot;
... /&gt;&#39;&#39;&#39;)
</pre></div>
</div>
Again, it&#8217;s business as usual with an unproxied object:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; subscribers = zope.component.subscribers((content, a1), IS)
&gt;&gt;&gt; a3 = subscribers[0]
&gt;&gt;&gt; a3.__class__ is A3
True
&gt;&gt;&gt; a3.context == (content, a1)
True
&gt;&gt;&gt; type(a3) is A3
True
</pre></div>
</div>
With a proxied object, we again get a security-proxied subscriber:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; p = ProxyFactory(content)
&gt;&gt;&gt; a3 = zope.component.subscribers((p, a1), IS)[0]

&gt;&gt;&gt; type(a3)
&lt;type &#39;zope.security._proxy._Proxy&#39;&gt;

&gt;&gt;&gt; removeSecurityProxy(a3).context[0] is content
True
</pre></div>
</div>
However, thanks to the <tt class="docutils literal">locate</tt> argument, we now have a location
proxy behind the security proxy:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; type(removeSecurityProxy(a3))
&lt;class &#39;zope.location.location.LocationProxy&#39;&gt;
</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>
Sometimes, subscribers don&#8217;t need to be adapters that actually provide
anything. It&#8217;s enough that a callable is called for a certain event.
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;subscriber
... for=&quot;zope.component.testfiles.components.IContent
... zope.component.testfiles.adapter.I1&quot;
... handler=&quot;zope.component.testfiles.adapter.Handler&quot;
... /&gt;&#39;&#39;&#39;)
</pre></div>
</div>
In this case, simply getting the subscribers is enough to invoke them:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; list(zope.component.subscribers((content, a1), None))
[]
&gt;&gt;&gt; content.args == ((a1,),)
True
</pre></div>
</div>
</div>
</div>
<div class="section" id="utility">
<h2>utility<a class="headerlink" href="#utility" title="Permalink to this headline">¶</a></h2>
Apart from adapters (and subscription adapters), the Component
Architecture knows a second kind of component: utilities. They are
registered using the &lt;utility /&gt; directive.
Before we register the first test utility, we can verify that utility
lookup doesn&#8217;t work yet:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; zope.component.queryUtility(IApp) is None
True
</pre></div>
</div>
Then we register the utility:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;utility
... component=&quot;zope.component.testfiles.components.comp&quot;
... provides=&quot;zope.component.testfiles.components.IApp&quot;
... /&gt;&#39;&#39;&#39;)
&gt;&gt;&gt; zope.component.getUtility(IApp) is comp
True
</pre></div>
</div>
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.
First, we make sure that there&#8217;s no utility yet:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; zope.component.queryUtility(IApp, &#39;test&#39;) is None
True
</pre></div>
</div>
Then we register it:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;utility
... component=&quot;zope.component.testfiles.components.comp&quot;
... provides=&quot;zope.component.testfiles.components.IApp&quot;
... name=&quot;test&quot;
... /&gt;&#39;&#39;&#39;)
&gt;&gt;&gt; zope.component.getUtility(IApp, &#39;test&#39;) is comp
True
</pre></div>
</div>
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&#8217;d pass a class for
the factory:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; zope.component.queryUtility(IApp) is None
True

&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;utility
... factory=&quot;zope.component.testfiles.components.Comp&quot;
... provides=&quot;zope.component.testfiles.components.IApp&quot;
... /&gt;&#39;&#39;&#39;)
&gt;&gt;&gt; zope.component.getUtility(IApp).__class__ is Comp
True
</pre></div>
</div>
<div class="section" id="declaring-provides-in-python">
<h3>Declaring <tt class="docutils literal">provides</tt> in Python<a class="headerlink" href="#declaring-provides-in-python" title="Permalink to this headline">¶</a></h3>
Like other directives, &lt;utility /&gt; can also figure out which interface
a utility provides from the Python declaration:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; zope.component.queryUtility(IApp) is None
True

&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;utility component=&quot;zope.component.testfiles.components.comp&quot; /&gt;&#39;&#39;&#39;)
&gt;&gt;&gt; zope.component.getUtility(IApp) is comp
True
</pre></div>
</div>
It won&#8217;t work if the component that is to be registered doesn&#8217;t
provide anything:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;utility component=&quot;zope.component.testfiles.adapter.a4&quot; /&gt;&#39;&#39;&#39;)
Traceback (most recent call last):
 ...
ZopeXMLConfigurationError: File &quot;&lt;string&gt;&quot;, line 4.2-4.61
 TypeError: Missing &#39;provides&#39; attribute
</pre></div>
</div>
Or if more than one interface is provided (then the ZCML directive
handler doesn&#8217;t know under which the utility should be registered):
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;utility component=&quot;zope.component.testfiles.adapter.a5&quot; /&gt;&#39;&#39;&#39;)
Traceback (most recent call last):
 ...
ZopeXMLConfigurationError: File &quot;&lt;string&gt;&quot;, line 4.2-4.61
 TypeError: Missing &#39;provides&#39; attribute
</pre></div>
</div>
We can repeat the same drill for utility factories:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;utility factory=&quot;zope.component.testfiles.components.Comp&quot; /&gt;&#39;&#39;&#39;)
&gt;&gt;&gt; zope.component.getUtility(IApp).__class__ is Comp
True

&gt;&gt;&gt; clearZCML()
&gt;&gt;&gt; runSnippet(&#39;&#39;&#39;
... &lt;utility factory=&quot;zope.component.testfiles.adapter.A5&quot; /&gt;&#39;&#39;&#39;)
Traceback (most recent call last):
 ...
ZopeXMLConfigurationError: File &quot;&lt;string&gt;&quot;, line 4.2-4.59
 TypeError: Missing &#39;provides&#39; attribute
</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>
TODO:
<div class="highlight-python"><div class="highlight"><pre>def testProtectedUtility(self):
 &quot;&quot;&quot;Test that we can protect a utility.

Also:
 Check that multiple configurations for the same utility and
 don&#39;t interfere.
 &quot;&quot;&quot;
 self.assertEqual(zope.component.queryUtility(IV), None)
 xmlconfig(StringIO(template % (
 &#39;&#39;&#39;
 &lt;permission id=&quot;tell.everyone&quot; title=&quot;Yay&quot; /&gt;
 &lt;utility
 component=&quot;zope.component.testfiles.components.comp&quot;
 provides=&quot;zope.component.testfiles.components.IApp&quot;
 permission=&quot;tell.everyone&quot;
 /&gt;
 &lt;permission id=&quot;top.secret&quot; title=&quot;shhhh&quot; /&gt;
 &lt;utility
 component=&quot;zope.component.testfiles.components.comp&quot;
 provides=&quot;zope.component.testfiles.components.IAppb&quot;
 permission=&quot;top.secret&quot;
 /&gt;
 &#39;&#39;&#39;
 )))

utility = ProxyFactory(zope.component.getUtility(IApp))
 items = getTestProxyItems(utility)
 self.assertEqual(items, [(&#39;a&#39;, &#39;tell.everyone&#39;),
 (&#39;f&#39;, &#39;tell.everyone&#39;)
 ])
 self.assertEqual(removeSecurityProxy(utility), comp)

def testUtilityUndefinedPermission(self):
 config = StringIO(template % (
 &#39;&#39;&#39;
 &lt;utility
 component=&quot;zope.component.testfiles.components.comp&quot;
 provides=&quot;zope.component.testfiles.components.IApp&quot;
 permission=&quot;zope.UndefinedPermission&quot;
 /&gt;
 &#39;&#39;&#39;
 ))
 self.assertRaises(ValueError, xmlconfig, config,
 testing=1)
</pre></div>
</div>
</div>
</div>
<div class="section" id="interface">
<h2>interface<a class="headerlink" href="#interface" title="Permalink to this headline">¶</a></h2>
The &lt;interface /&gt; directive lets us register an interface. Interfaces
are registered as named utilities. We therefore needn&#8217;t go though all
the lookup details again, it is sufficient to see whether the
directive handler emits the right actions.
First we provide a stub configuration context:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; import re, pprint
&gt;&gt;&gt; atre = re.compile(&#39; at [0-9a-fA-Fx]+&#39;)
&gt;&gt;&gt; class Context(object):
... actions = ()
... def action(self, discriminator, callable, args):
... self.actions += ((discriminator, callable, args), )
... def __repr__(self):
... stream = StringIO()
... pprinter = pprint.PrettyPrinter(stream=stream, width=60)
... pprinter.pprint(self.actions)
... r = stream.getvalue()
... return (&#39;&#39;.join(atre.split(r))).strip()
&gt;&gt;&gt; context = Context()
</pre></div>
</div>
Then we provide a test interface that we&#8217;d like to register:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; from zope.interface import Interface
&gt;&gt;&gt; class I(Interface):
... pass
</pre></div>
</div>
It doesn&#8217;t yet provide <tt class="docutils literal">ITestType</tt>:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; from zope.component.tests.examples import ITestType
&gt;&gt;&gt; ITestType.providedBy(I)
False
</pre></div>
</div>
However, after calling the directive handler...
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; from zope.component.zcml import interface
&gt;&gt;&gt; interface(context, I, ITestType)
&gt;&gt;&gt; context
((None,
 &lt;function provideInterface&gt;,
 (&#39;&#39;,
 &lt;InterfaceClass __builtin__.I&gt;,
 &lt;InterfaceClass zope.component.tests.examples.ITestType&gt;)),)
</pre></div>
</div>
...it does provide <tt class="docutils literal">ITestType</tt>:
<div class="highlight-python"><div class="highlight"><pre>&gt;&gt;&gt; from zope.interface.interfaces import IInterface
&gt;&gt;&gt; ITestType.extends(IInterface)
True
&gt;&gt;&gt; IInterface.providedBy(I)
True
</pre></div>
</div>
</div>
</div>

</div>
 </div>
 </div>
 <div class="sphinxsidebar">
 <div class="sphinxsidebarwrapper">
 <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">for</tt> and <tt class="docutils literal">provides</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">for</tt> and <tt class="docutils literal">provides</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">provides</tt> in Python</a></li>
<li><a class="reference internal" href="#protected-utilities">Protected utilities</a></li>
</ul>
</li>
<li><a class="reference internal" href="#interface">interface</a></li>
</ul>
</li>
</ul>

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