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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>Events — zope.configuration 4.0 documentation</title> <link rel="stylesheet" href="_static/default.css" type="text/css" /> <link rel="stylesheet" href="_static/pygments.css" type="text/css" /> <script type="text/javascript"> var DOCUMENTATION_OPTIONS = { URL_ROOT: '', VERSION: '4.0', COLLAPSE_INDEX: false, FILE_SUFFIX: '.html', HAS_SOURCE: true }; </script> <script type="text/javascript" src="_static/jquery.js"></script> <script type="text/javascript" src="_static/underscore.js"></script> <script type="text/javascript" src="_static/doctools.js"></script> <link rel="top" title="zope.configuration 4.0 documentation" href="index.html" /> <link rel="next" title="Factories" href="factory.html" /> <link rel="prev" title="The Zope 3 Component Architecture (Socket Example)" href="socketexample.html" /> </head> <body> <div class="related"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="genindex.html" title="General Index" accesskey="I">index</a></li> <li class="right" > <a href="factory.html" title="Factories" accesskey="N">next</a> |</li> <li class="right" > <a href="socketexample.html" title="The Zope 3 Component Architecture (Socket Example)" accesskey="P">previous</a> |</li> <li><a href="index.html">zope.configuration 4.0 documentation</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body"> <div class="section" id="events"> <h1>Events<a class="headerlink" href="#events" title="Permalink to this headline">¶</a></h1> <p>The Component Architecture provides a way to dispatch events to event handlers. Event handlers are registered as <em>subscribers</em> a.k.a. <em>handlers</em>.</p> <p>Before we can start we need to import <tt class="docutils literal"><span class="pre">zope.component.event</span></tt> to make the dispatching effective:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">zope.component.event</span> </pre></div> </div> <p>Consider two event classes:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="k">class</span> <span class="nc">Event1</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span> <span class="gp">... </span> <span class="k">pass</span> <span class="gp">>>> </span><span class="k">class</span> <span class="nc">Event2</span><span class="p">(</span><span class="n">Event1</span><span class="p">):</span> <span class="gp">... </span> <span class="k">pass</span> </pre></div> </div> <p>Now consider two handlers for these event classes:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">called</span> <span class="o">=</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="nd">@zope.component.adapter</span><span class="p">(</span><span class="n">Event1</span><span class="p">)</span> <span class="gp">... </span><span class="k">def</span> <span class="nf">handler1</span><span class="p">(</span><span class="n">event</span><span class="p">):</span> <span class="gp">... </span> <span class="n">called</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span> <span class="gp">>>> </span><span class="nd">@zope.component.adapter</span><span class="p">(</span><span class="n">Event2</span><span class="p">)</span> <span class="gp">... </span><span class="k">def</span> <span class="nf">handler2</span><span class="p">(</span><span class="n">event</span><span class="p">):</span> <span class="gp">... </span> <span class="n">called</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="mi">2</span><span class="p">)</span> </pre></div> </div> <p>We can register them with the Component Architecture:</p> <div class="highlight-python"><div class="highlight"><pre><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">provideHandler</span><span class="p">(</span><span class="n">handler1</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">provideHandler</span><span class="p">(</span><span class="n">handler2</span><span class="p">)</span> </pre></div> </div> <p>Now let’s go through the events. We’ll see that the handlers have been called accordingly:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.event</span> <span class="kn">import</span> <span class="n">notify</span> <span class="gp">>>> </span><span class="n">notify</span><span class="p">(</span><span class="n">Event1</span><span class="p">())</span> <span class="gp">>>> </span><span class="n">called</span> <span class="go">[1]</span> <span class="gp">>>> </span><span class="k">del</span> <span class="n">called</span><span class="p">[:]</span> <span class="gp">>>> </span><span class="n">notify</span><span class="p">(</span><span class="n">Event2</span><span class="p">())</span> <span class="gp">>>> </span><span class="n">called</span><span class="o">.</span><span class="n">sort</span><span class="p">()</span> <span class="gp">>>> </span><span class="n">called</span> <span class="go">[1, 2]</span> </pre></div> </div> <div class="section" id="object-events"> <h2>Object events<a class="headerlink" href="#object-events" title="Permalink to this headline">¶</a></h2> <p>The <tt class="docutils literal"><span class="pre">objectEventNotify</span></tt> function is a subscriber to dispatch ObjectEvents to interested adapters.</p> <p>First create an object class:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="k">class</span> <span class="nc">IUseless</span><span class="p">(</span><span class="n">zope</span><span class="o">.</span><span class="n">interface</span><span class="o">.</span><span class="n">Interface</span><span class="p">):</span> <span class="gp">... </span> <span class="sd">"""Useless object"""</span> <span class="gp">>>> </span><span class="k">class</span> <span class="nc">UselessObject</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span> <span class="gp">... </span> <span class="sd">"""Useless object"""</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">IUseless</span><span class="p">)</span> </pre></div> </div> <p>Then create an event class:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="k">class</span> <span class="nc">IObjectThrownEvent</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">interfaces</span><span class="o">.</span><span class="n">IObjectEvent</span><span class="p">):</span> <span class="gp">... </span> <span class="sd">"""An object has been thrown away"""</span> <span class="gp">>>> </span><span class="k">class</span> <span class="nc">ObjectThrownEvent</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">interfaces</span><span class="o">.</span><span class="n">ObjectEvent</span><span class="p">):</span> <span class="gp">... </span> <span class="sd">"""An object has been thrown away"""</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">IObjectThrownEvent</span><span class="p">)</span> </pre></div> </div> <p>Create an object and an event:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">hammer</span> <span class="o">=</span> <span class="n">UselessObject</span><span class="p">()</span> <span class="gp">>>> </span><span class="n">event</span> <span class="o">=</span> <span class="n">ObjectThrownEvent</span><span class="p">(</span><span class="n">hammer</span><span class="p">)</span> </pre></div> </div> <p>Then notify the event to the subscribers. Since the subscribers list is empty, nothing happens.</p> <div class="highlight-python"><div class="highlight"><pre><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">event</span><span class="o">.</span><span class="n">objectEventNotify</span><span class="p">(</span><span class="n">event</span><span class="p">)</span> </pre></div> </div> <p>Now create an handler for the event:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">events</span> <span class="o">=</span> <span class="p">[]</span> <span class="gp">>>> </span><span class="k">def</span> <span class="nf">record</span><span class="p">(</span><span class="o">*</span><span class="n">args</span><span class="p">):</span> <span class="c">#*</span> <span class="gp">... </span> <span class="n">events</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">args</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">provideHandler</span><span class="p">(</span><span class="n">record</span><span class="p">,</span> <span class="p">[</span><span class="n">IUseless</span><span class="p">,</span> <span class="n">IObjectThrownEvent</span><span class="p">])</span> </pre></div> </div> <p>The event is notified to the subscriber:</p> <div class="highlight-python"><div class="highlight"><pre><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">event</span><span class="o">.</span><span class="n">objectEventNotify</span><span class="p">(</span><span class="n">event</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">events</span> <span class="o">==</span> <span class="p">[(</span><span class="n">hammer</span><span class="p">,</span> <span class="n">event</span><span class="p">)]</span> <span class="go">True</span> </pre></div> </div> <p>Following test demonstrates how a subscriber can raise an exception to prevent an action.</p> <div class="highlight-python"><div class="highlight"><pre><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">provideHandler</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">event</span><span class="o">.</span><span class="n">objectEventNotify</span><span class="p">)</span> </pre></div> </div> <p>Let’s create a container:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="k">class</span> <span class="nc">ToolBox</span><span class="p">(</span><span class="nb">dict</span><span class="p">):</span> <span class="gp">... </span> <span class="k">def</span> <span class="nf">__delitem__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">key</span><span class="p">):</span> <span class="gp">... </span> <span class="n">notify</span><span class="p">(</span><span class="n">ObjectThrownEvent</span><span class="p">(</span><span class="bp">self</span><span class="p">[</span><span class="n">key</span><span class="p">]))</span> <span class="gp">... </span> <span class="k">return</span> <span class="nb">super</span><span class="p">(</span><span class="n">ToolBox</span><span class="p">,</span><span class="bp">self</span><span class="p">)</span><span class="o">.</span><span class="n">__delitem__</span><span class="p">(</span><span class="n">key</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">container</span> <span class="o">=</span> <span class="n">ToolBox</span><span class="p">()</span> </pre></div> </div> <p>And put the object into the container:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">container</span><span class="p">[</span><span class="s">'Red Hammer'</span><span class="p">]</span> <span class="o">=</span> <span class="n">hammer</span> </pre></div> </div> <p>Create an handler function that will raise an error when called:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="k">class</span> <span class="nc">Veto</span><span class="p">(</span><span class="ne">Exception</span><span class="p">):</span> <span class="gp">... </span> <span class="k">pass</span> <span class="gp">>>> </span><span class="k">def</span> <span class="nf">callback</span><span class="p">(</span><span class="n">item</span><span class="p">,</span> <span class="n">event</span><span class="p">):</span> <span class="gp">... </span> <span class="k">assert</span><span class="p">(</span><span class="n">item</span> <span class="o">==</span> <span class="n">event</span><span class="o">.</span><span class="n">object</span><span class="p">)</span> <span class="gp">... </span> <span class="k">raise</span> <span class="n">Veto</span> </pre></div> </div> <p>Register the handler:</p> <div class="highlight-python"><div class="highlight"><pre><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">provideHandler</span><span class="p">(</span><span class="n">callback</span><span class="p">,</span> <span class="p">[</span><span class="n">IUseless</span><span class="p">,</span> <span class="n">IObjectThrownEvent</span><span class="p">])</span> </pre></div> </div> <p>Then if we try to remove the object, an ObjectThrownEvent is fired:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="k">del</span> <span class="n">container</span><span class="p">[</span><span class="s">'Red Hammer'</span><span class="p">]</span> <span class="gp">... </span> <span class="gt">Traceback (most recent call last):</span> <span class="c">...</span> <span class="k">raise</span> <span class="n">Veto</span> <span class="gr">Veto</span> </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="#">Events</a><ul> <li><a class="reference internal" href="#object-events">Object events</a></li> </ul> </li> </ul> <h4>Previous topic</h4> <p class="topless"><a href="socketexample.html" title="previous chapter">The Zope 3 Component Architecture (Socket Example)</a></p> <h4>Next topic</h4> <p class="topless"><a href="factory.html" title="next chapter">Factories</a></p> <h3>This Page</h3> <ul class="this-page-menu"> <li><a href="_sources/event.txt" rel="nofollow">Show 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