3db9ce0bf0
git-svn-id: svn://svn.cy55.de/Zope3/src/cybertools/trunk@1545 fd906abe-77d9-0310-91a1-e0d9ade77398
59 lines
1.7 KiB
Text
59 lines
1.7 KiB
Text
==================
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Deferred Execution
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==================
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$Id$
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>>> from cybertools.util.defer import Deferred
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To show what deferreds are about we need two classes.
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The first one will be doing some time-consuming work, or may be it waits
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for some event - as in this case simulated by calling the `nowItsTime()`
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method. As the function or object that calls the `work()` method
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- let's call it the client should not have to wait, this method immediately
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returns a Deferred object.
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Later on, when the work is finished, the Deferred's `callback()`
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method will be called, thus notifying the client.
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>>> class Worker(object):
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...
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... def work(self):
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... self.deferred = Deferred()
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... print 'Worker: work started'
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... return self.deferred
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...
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... def nowItsTime(self):
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... self.deferred.callback('Work completed')
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The second class, the client, gives the worker object some work;
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in order to get notified when the work is finished it registers a
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callback method with the deferred object coming back from the
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`work()` call.
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>>> class Client(object):
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...
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... def run(self, worker):
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... deferred = worker.work()
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... deferred.addCallback(self.showResult)
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... print 'Client: The worker seems to be working now...'
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...
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... def showResult(self, result):
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... print 'Result:', result
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So we now create a worker and a client, and let the client run:
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>>> w = Worker()
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>>> client = Client()
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>>> client.run(w)
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Worker: work started
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Client: The worker seems to be working now...
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Working, working,...
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Work will be completed when its time:
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>>> w.nowItsTime()
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Result: Work completed
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