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<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 <code class="docutils literal notranslate"><span class="pre">zope.component.event</span></code> to make
the dispatching effective:</p>
<p>Consider two event classes:</p>
<p>Now consider two handlers for these event classes:</p>
<p>We can register them with the Component Architecture:</p>
<p>Now let’s go through the events. We’ll see that the handlers have been
called accordingly:</p>
<div class="section" id="object-events">
<h2>Object events<a class="headerlink" href="#object-events" title="Permalink to this headline">¶</a></h2>
<p>The <code class="docutils literal notranslate"><span class="pre">objectEventNotify</span></code> function is a subscriber to dispatch
ObjectEvents to interested adapters.</p>
<p>First create an object class:</p>
<p>Then create an event class:</p>
<p>Create an object and an event:</p>
<p>Then notify the event to the subscribers.
Since the subscribers list is empty, nothing happens.</p>
<p>Now create an handler for the event:</p>
<p>The event is notified to the subscriber:</p>
<p>Following test demonstrates how a subscriber can raise an exception
to prevent an action.</p>
<p>Let’s create a container:</p>
<p>And put the object into the container:</p>
<p>Create an handler function that will raise an error when called:</p>
<p>Register the handler:</p>
<p>Then if we try to remove the object, an ObjectThrownEvent is fired:</p>
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