added simple Deferred implementation

git-svn-id: svn://svn.cy55.de/Zope3/src/cybertools/trunk@1545 fd906abe-77d9-0310-91a1-e0d9ade77398

storage/pzope/base.py

@@ -92,7 +92,7 @@ class Adapter(object):
             self.address = getPath(persistent)
         else:
             if self.address is None:
-                self.address = address  # lets
+                self.address = address
             else:
                 address = self.address
             persistent = traverse(getSite(), address)

util/defer.py

@@ -0,0 +1,36 @@
+#
+#  Copyright (c) 2007 Helmut Merz helmutm@cy55.de
+#
+#  This program is free software; you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation; either version 2 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program; if not, write to the Free Software
+#  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+#
+
+"""
+A simple Deferred implementation.
+
+$Id$
+"""
+
+class Deferred(object):
+
+    def __init__(self):
+        self._callbacks = []
+
+    def callback(self, *args, **kw):
+        for f in self._callbacks:
+            f(*args, **kw)
+
+    def addCallback(self, function):
+        self._callbacks.append(function)
+        return self

util/defer.txt

@@ -0,0 +1,59 @@
+==================
+Deferred Execution
+==================
+
+$Id$
+
+  >>> from cybertools.util.defer import Deferred
+
+To show what deferreds are about we need two classes.
+
+The first one will be doing some time-consuming work, or may be it waits
+for some event - as in this case simulated by calling the `nowItsTime()`
+method. As the function or object that calls the `work()` method
+- let's call it the client should not have to wait, this method immediately
+returns a Deferred object.
+
+Later on, when the work is finished, the Deferred's `callback()`
+method will be called, thus notifying the client.
+
+  >>> class Worker(object):
+  ...
+  ...     def work(self):
+  ...         self.deferred = Deferred()
+  ...         print 'Worker: work started'
+  ...         return self.deferred
+  ...
+  ...     def nowItsTime(self):
+  ...         self.deferred.callback('Work completed')
+
+The second class, the client, gives the worker object some work;
+in order to get notified when the work is finished it registers a
+callback method with the deferred object coming back from the
+`work()` call.
+
+  >>> class Client(object):
+  ...
+  ...     def run(self, worker):
+  ...         deferred = worker.work()
+  ...         deferred.addCallback(self.showResult)
+  ...         print 'Client: The worker seems to be working now...'
+  ...
+  ...     def showResult(self, result):
+  ...         print 'Result:', result
+
+So we now create a worker and a client, and let the client run:
+
+  >>> w = Worker()
+  >>> client = Client()
+  >>> client.run(w)
+  Worker: work started
+  Client: The worker seems to be working now...
+
+Working, working,...
+
+Work will be completed when its time:
+
+  >>> w.nowItsTime()
+  Result: Work completed
+

util/tests.py

@@ -19,6 +19,7 @@ def test_suite():
         #unittest.makeSuite(Test),  # we don't need this
         #doctest.DocTestSuite(cybertools.util.property, optionflags=flags),
         doctest.DocFileSuite('adapter.txt', optionflags=flags),
+        doctest.DocFileSuite('defer.txt', optionflags=flags),
         doctest.DocFileSuite('property.txt', optionflags=flags),
         ))