http://code.activestate.com/recipes/tags/reactive/views/2012-02-14T23:43:53-08:00ActiveState Code Recipes2012-02-14T23:43:53-08:00Rodney Drenthhttp://code.activestate.com/recipes/users/4050661/http://code.activestate.com/recipes/578038-observer-pattern-implemented-with-descriptor-class/

<p style="color: grey"> Python recipe 578038 by <a href="/recipes/users/4050661/">Rodney Drenth</a> (<a href="/recipes/tags/descriptor/">descriptor</a>, <a href="/recipes/tags/observer/">observer</a>, <a href="/recipes/tags/publish/">publish</a>, <a href="/recipes/tags/reactive/">reactive</a>, <a href="/recipes/tags/subscribe/">subscribe</a>). </p> <p>The observer pattern is implemented using an observable descriptor. One creates instances of observable in a class, which allows observers to subscribe to changes in the observable. Assigning a value to the observable causes the suscribers to be notified. An observable can subscribe to another observable, in which case changes to the second propagate to subscribers of the first. The subscribe method returns a Subscription object. When this object is deleted or becomes unreferenced, the subscription is cancelled.</p> <p>This version compatible with Python 3.0 Example uses unittest to help in understanding the functionality.</p>