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<div class="section" id="module-other.pubsub">
<h1>pubsub<a class="headerlink" href="#module-other.pubsub" title="Permalink to this headline">¶</a></h1>
<p>This module provides a publish-subscribe component that allows
listeners to subcribe to messages of a given topic. Contrary to the
original wxPython.lib.pubsub module (which it is based on), it uses
weak referencing to the subscribers so the lifetime of subscribers
is not affected by Publisher. Also, callable objects can be used in
addition to functions and bound methods. See Publisher class docs for
more details.</p>
<p>Thanks to Robb Shecter and Robin Dunn for having provided
the basis for this module (which now shares most of the concepts but
very little design or implementation with the original
wxPython.lib.pubsub).</p>
<p>The publisher is a singleton instance of the PublisherClass class. You
access the instance via the Publisher object available from the module:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">wx.lib.pubsub</span> <span class="kn">import</span> <span class="n">Publisher</span>
<span class="n">Publisher</span><span class="p">()</span><span class="o">.</span><span class="n">subscribe</span><span class="p">(</span><span class="o">...</span><span class="p">)</span>
<span class="n">Publisher</span><span class="p">()</span><span class="o">.</span><span class="n">sendMessage</span><span class="p">(</span><span class="o">...</span><span class="p">)</span>
<span class="o">...</span>
</pre></div>
</div>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Author:</th><td class="field-body">Oliver Schoenborn</td>
</tr>
<tr class="field"><th class="field-name">Since:</th><td class="field-body">Apr 2004</td>
</tr>
<tr class="field"><th class="field-name">Version:</th><td class="field-body">$Id: pubsub.py,v 1.8 2006/06/11 00:12:59 RD Exp $</td>
</tr>
<tr class="field"><th class="field-name">Copyright:</th><td class="field-body">(c) 2004 Oliver Schoenborn</td>
</tr>
<tr class="field"><th class="field-name">License:</th><td class="field-body">wxWidgets</td>
</tr>
</tbody>
</table>
<dl class="class">
<dt id="other.pubsub.Message">
<em class="property">
class </em><tt class="descclassname">other.pubsub.</tt><tt class="descname">Message</tt><big>(</big><em>topic</em>, <em>data</em><big>)</big><a class="headerlink" href="#other.pubsub.Message" title="Permalink to this definition">¶</a></dt>
<dd>A simple container object for the two components of a message: the
topic and the user data. An instance of Message is given to your
listener when called by Publisher().sendMessage(topic) (if your
listener callback was registered for that topic).</dd></dl>
<dl class="class">
<dt id="other.pubsub.PublisherClass">
<em class="property">
class </em><tt class="descclassname">other.pubsub.</tt><tt class="descname">PublisherClass</tt><big>(</big><em>singletonKey</em><big>)</big><a class="headerlink" href="#other.pubsub.PublisherClass" title="Permalink to this definition">¶</a></dt>
<dd><p>The publish/subscribe manager. It keeps track of which listeners
are interested in which topics (see subscribe()), and sends a
Message for a given topic to listeners that have subscribed to
that topic, with optional user data (see sendMessage()).</p>
<p>The three important concepts for Publisher are:</p>
<ul>
<li><p class="first">listener: a function, bound method or
callable object that can be called with one parameter
(not counting ‘self’ in the case of methods). The parameter
will be a reference to a Message object. E.g., these listeners
are ok:</p>
<div class="highlight-python"><pre>class Foo:
def __call__(self, a, b=1): pass # can be called with only one arg
def meth(self, a): pass # takes only one arg
def meth2(self, a=2, b=''): pass # can be called with one arg
def func(a, b=''): pass
Foo foo
Publisher().subscribe(foo) # functor
Publisher().subscribe(foo.meth) # bound method
Publisher().subscribe(foo.meth2) # bound method
Publisher().subscribe(func) # function</pre>
</div>
<p>The three types of callables all have arguments that allow a call
with only one argument. In every case, the parameter ‘a’ will contain
the message.</p>
</li>
<li><p class="first">topic: a single word, a tuple of words, or a string containing a
set of words separated by dots, for example: ‘sports.baseball’.
A tuple or a dotted notation string denotes a hierarchy of
topics from most general to least. For example, a listener of
this topic:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="p">(</span><span class="s">'sports'</span><span class="p">,</span><span class="s">'baseball'</span><span class="p">)</span>
</pre></div>
</div>
<p>would receive messages for these topics:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="p">(</span><span class="s">'sports'</span><span class="p">,</span> <span class="s">'baseball'</span><span class="p">)</span> <span class="c"># because same</span>
<span class="p">(</span><span class="s">'sports'</span><span class="p">,</span> <span class="s">'baseball'</span><span class="p">,</span> <span class="s">'highscores'</span><span class="p">)</span> <span class="c"># because more specific</span>
</pre></div>
</div>
<p>but not these:</p>
<div class="highlight-python"><pre> 'sports' # because more general
('sports',) # because more general
() or ('') # because only for those listening to 'all' topics
('news') # because different topic</pre>
</div>
</li>
<li><p class="first">message: this is an instance of Message, containing the topic for
which the message was sent, and any data the sender specified.</p>
</li>
</ul>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Note:</th><td class="field-body">This class is visible to importers of pubsub only as a
Singleton. I.e., every time you execute ‘Publisher()’, it’s
actually the same instance of PublisherClass that is
returned. So to use, just do’Publisher().method()’.</td>
</tr>
</tbody>
</table>
<dl class="method">
<dt id="other.pubsub.PublisherClass.getAssociatedTopics">
<tt class="descname">getAssociatedTopics</tt><big>(</big><em>listener</em><big>)</big><a class="headerlink" href="#other.pubsub.PublisherClass.getAssociatedTopics" title="Permalink to this definition">¶</a></dt>
<dd><p>Return a list of topics the given listener is registered with.
Returns [] if listener never subscribed.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Attention:</th><td class="field-body"><p class="first">when using the return of this method to compare to
expected list of topics, remember that topics that are
not in the form of a tuple appear as a one-tuple in
the return. E.g. if you have subscribed a listener to
‘topic1’ and (‘topic2’,’subtopic2’), this method
returns:</p>
<p class="last">associatedTopics = [(‘topic1’,), (‘topic2’,’subtopic2’)]</p>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="method">
<dt id="other.pubsub.PublisherClass.getDeliveryCount">
<tt class="descname">getDeliveryCount</tt><big>(</big><big>)</big><a class="headerlink" href="#other.pubsub.PublisherClass.getDeliveryCount" title="Permalink to this definition">¶</a></dt>
<dd>How many listeners have received a message since beginning of run</dd></dl>
<dl class="method">
<dt id="other.pubsub.PublisherClass.getMessageCount">
<tt class="descname">getMessageCount</tt><big>(</big><big>)</big><a class="headerlink" href="#other.pubsub.PublisherClass.getMessageCount" title="Permalink to this definition">¶</a></dt>
<dd>How many times sendMessage() was called since beginning of run</dd></dl>
<dl class="method">
<dt id="other.pubsub.PublisherClass.isSubscribed">
<tt class="descname">isSubscribed</tt><big>(</big><em>listener</em>, <em>topic=None</em><big>)</big><a class="headerlink" href="#other.pubsub.PublisherClass.isSubscribed" title="Permalink to this definition">¶</a></dt>
<dd>Return true if listener has subscribed to topic specified.
If no topic specified, return true if subscribed to something.
Use topic=getStrAllTopics() to determine if a listener will receive
messages for all topics.</dd></dl>
<dl class="method">
<dt id="other.pubsub.PublisherClass.isValid">
<tt class="descname">isValid</tt><big>(</big><em>listener</em><big>)</big><a class="headerlink" href="#other.pubsub.PublisherClass.isValid" title="Permalink to this definition">¶</a></dt>
<dd>Return true only if listener will be able to subscribe to
Publisher.</dd></dl>
<dl class="method">
<dt id="other.pubsub.PublisherClass.sendMessage">
<tt class="descname">sendMessage</tt><big>(</big><em>topic=''</em>, <em>data=None</em>, <em>onTopicNeverCreated=None</em><big>)</big><a class="headerlink" href="#other.pubsub.PublisherClass.sendMessage" title="Permalink to this definition">¶</a></dt>
<dd>Send a message for given topic, with optional data, to
subscribed listeners. If topic is not specified, only the
listeners that are interested in all topics will receive message.
The onTopicNeverCreated is an optional callback of your choice that
will be called if the topic given was never created (i.e. it, or
one of its subtopics, was never subscribed to by any listener).
It will be called as onTopicNeverCreated(topic).</dd></dl>
<dl class="method">
<dt id="other.pubsub.PublisherClass.subscribe">
<tt class="descname">subscribe</tt><big>(</big><em>listener</em>, <em>topic=''</em><big>)</big><a class="headerlink" href="#other.pubsub.PublisherClass.subscribe" title="Permalink to this definition">¶</a></dt>
<dd><p>Subscribe listener for given topic. If topic is not specified,
listener will be subscribed for all topics (that listener will
receive a Message for any topic for which a message is generated).</p>
<p>This method may be called multiple times for one listener,
registering it with many topics. It can also be invoked many
times for a particular topic, each time with a different
listener. See the class doc for requirements on listener and
topic.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field"><th class="field-name">Note:</th><td class="field-body"><p class="first">The listener is held by Publisher() only by <em>weak</em>
reference. This means you must ensure you have at
least one strong reference to listener, otherwise it
will be DOA (“dead on arrival”). This is particularly
easy to forget when wrapping a listener method in a
proxy object (e.g. to bind some of its parameters),
e.g.:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="k">class</span> <span class="nc">Foo</span><span class="p">:</span>
<span class="k">def</span> <span class="nf">listener</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">event</span><span class="p">):</span> <span class="k">pass</span>
<span class="k">class</span> <span class="nc">Wrapper</span><span class="p">:</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">fun</span><span class="p">):</span> <span class="bp">self</span><span class="o">.</span><span class="n">fun</span> <span class="o">=</span> <span class="n">fun</span>
<span class="k">def</span> <span class="nf">__call__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">):</span> <span class="bp">self</span><span class="o">.</span><span class="n">fun</span><span class="p">(</span><span class="o">*</span><span class="n">args</span><span class="p">)</span>
<span class="n">foo</span> <span class="o">=</span> <span class="n">Foo</span><span class="p">()</span>
<span class="n">Publisher</span><span class="p">()</span><span class="o">.</span><span class="n">subscribe</span><span class="p">(</span> <span class="n">Wrapper</span><span class="p">(</span><span class="n">foo</span><span class="o">.</span><span class="n">listener</span><span class="p">)</span> <span class="p">)</span> <span class="c"># whoops: DOA!</span>
<span class="n">wrapper</span> <span class="o">=</span> <span class="n">Wrapper</span><span class="p">(</span><span class="n">foo</span><span class="o">.</span><span class="n">listener</span><span class="p">)</span>
<span class="n">Publisher</span><span class="p">()</span><span class="o">.</span><span class="n">subscribe</span><span class="p">(</span><span class="n">wrapper</span><span class="p">)</span> <span class="c"># good!</span>
</pre></div>
</div>
</td>
</tr>
<tr class="field"><th class="field-name">Note:</th><td class="field-body"><p class="first last">Calling this method for the same listener, with two
topics in the same branch of the topic hierarchy, will
cause the listener to be notified twice when a message
for the deepest topic is sent. E.g.
subscribe(listener, ‘t1’) and then subscribe(listener,
(‘t1’,’t2’)) means that when calling sendMessage(‘t1’),
listener gets one message, but when calling
sendMessage((‘t1’,’t2’)), listener gets message twice.</p>
</td>
</tr>
</tbody>
</table>
</dd></dl>
<dl class="method">
<dt id="other.pubsub.PublisherClass.unsubAll">
<tt class="descname">unsubAll</tt><big>(</big><em>topics=None</em>, <em>onNoSuchTopic=None</em><big>)</big><a class="headerlink" href="#other.pubsub.PublisherClass.unsubAll" title="Permalink to this definition">¶</a></dt>
<dd>Unsubscribe all listeners subscribed for topics. Topics can
be a single topic (string or tuple) or a list of topics (ie
list containing strings and/or tuples). If topics is not
specified, all listeners for all topics will be unsubscribed,
ie. the Publisher singleton will have no topics and no listeners
left. If onNoSuchTopic is given, it will be called as
onNoSuchTopic(topic) for each topic that is unknown.</dd></dl>
<dl class="method">
<dt id="other.pubsub.PublisherClass.unsubscribe">
<tt class="descname">unsubscribe</tt><big>(</big><em>listener</em>, <em>topics=None</em><big>)</big><a class="headerlink" href="#other.pubsub.PublisherClass.unsubscribe" title="Permalink to this definition">¶</a></dt>
<dd><p>Unsubscribe listener. If topics not specified, listener is
completely unsubscribed. Otherwise, it is unsubscribed only
for the topic (the usual tuple) or list of topics (ie a list
of tuples) specified. Nothing happens if listener is not actually
subscribed to any of the topics.</p>
<p>Note that if listener subscribed for two topics (a,b) and (a,c),
then unsubscribing for topic (a) will do nothing. You must
use getAssociatedTopics(listener) and give unsubscribe() the returned
list (or a subset thereof).</p>
</dd></dl>
<dl class="method">
<dt id="other.pubsub.PublisherClass.validate">
<tt class="descname">validate</tt><big>(</big><em>listener</em><big>)</big><a class="headerlink" href="#other.pubsub.PublisherClass.validate" title="Permalink to this definition">¶</a></dt>
<dd>Similar to isValid(), but raises a TypeError exception if not valid</dd></dl>
</dd></dl>
<dl class="function">
<dt id="other.pubsub.getStrAllTopics">
<tt class="descclassname">other.pubsub.</tt><tt class="descname">getStrAllTopics</tt><big>(</big><big>)</big><a class="headerlink" href="#other.pubsub.getStrAllTopics" title="Permalink to this definition">¶</a></dt>
<dd>Function to call if, for whatever reason, you need to know
explicitely what is the string to use to indicate ‘all topics’.</dd></dl>
<dl class="function">
<dt id="other.pubsub.test">
<tt class="descclassname">other.pubsub.</tt><tt class="descname">test</tt><big>(</big><big>)</big><a class="headerlink" href="#other.pubsub.test" title="Permalink to this definition">¶</a></dt>
<dd></dd></dl>
</div>
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