proof-of-concept for a simple AOP implementation

git-svn-id: svn://svn.cy55.de/Zope3/src/cybertools/trunk@1961 fd906abe-77d9-0310-91a1-e0d9ade77398

util/aop.py

@@ -0,0 +1,76 @@
+#
+#  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
+#
+
+"""
+
+
+$Id$
+"""
+
+
+def getNotifier(method):
+    if isinstance(method, Notifier):
+        return method
+    return Notifier(method)
+
+
+class Notifier(object):
+
+    def __init__(self, method):
+        self.method = method
+        obj = method.im_self or method.im_class
+        name = method.im_func.func_name
+        setattr(obj, name, self)
+        self.beforeSubs = []
+        self.afterSubs = []
+
+    def __get__(self, instance, cls=None):
+        return BoundNotifier(self, instance)
+
+    def __call__(self, *args, **kw):
+        for sub, sargs, skw in self.beforeSubs:
+            sub(None, *sargs, **skw)
+        result = self.method(*args, **kw)
+        for sub, aargs, akw in self.afterSubs:
+            sub(result, *aargs, **akw)
+        return result
+
+    def subscribe(self, before, after, *args, **kw):
+        if before is not None:
+            self.beforeSubs.append((before, args, kw))
+        if after is not None:
+            self.afterSubs.append((after, args, kw))
+
+
+class BoundNotifier(object):
+
+    def __init__(self, context, instance):
+        self.context = context
+        self.instance = instance
+
+    def __call__(self, *args, **kw):
+        for sub, sargs, skw in self.context.beforeSubs:
+            sub(None, *sargs, **skw)
+        result = self.context.method(self.instance, *args, **kw)
+        for sub, aargs, akw in self.context.afterSubs:
+            sub(result, *aargs, **akw)
+        return result
+
+    def subscribe(self, before, after, *args, **kw):
+        self.context.subscribe(before, after, *args, **kw)
+

util/aop.txt

@@ -0,0 +1,64 @@
+=======================================
+Aspect-oriented Programming for Dummies
+=======================================
+
+$Id$
+
+  >>> from cybertools.util.aop import getNotifier
+
+  >>> class Demo(object):
+  ...     def foo(self, num):
+  ...         return 38 + num
+
+  >>> demo = Demo()
+  >>> demo.foo(4)
+  42
+
+  >>> wrappedFoo = getNotifier(demo.foo)
+  >>> demo.foo is wrappedFoo
+  True
+
+Repeated calls of ``getNotifier()`` return the same wrapped object.
+
+  >>> getNotifier(demo.foo) is wrappedFoo
+  True
+
+Calling the wrapped method still works.
+
+  >>> demo.foo(8)
+  46
+
+We can now get information about the returning of the method by
+subscribing to it using some log function.
+
+  >>> def log(result, msg):
+  ...     print 'logging: %s, result=%s' % (msg, str(result))
+
+  >>> demo.foo.subscribe(log, None, 'before foo')
+
+  >>> demo.foo(4)
+  logging: before foo, result=None
+  42
+
+  >>> demo.foo.subscribe(log, log, "that's foo")
+  >>> demo.foo(4)
+  logging: before foo, result=None
+  logging: that's foo, result=None
+  logging: that's foo, result=42
+  42
+
+
+Wrapping methods on class level
+===============================
+
+  >>> demo = Demo()
+  >>> demo.foo(4)
+  42
+
+  >>> getNotifier(Demo.foo)
+  <...Notifier object ...>
+  >>> Demo.foo.subscribe(None, log, 'after foo')
+  >>> demo.foo(4)
+  logging: after foo, result=42
+  42
+

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('aop.txt', optionflags=flags),
         doctest.DocFileSuite('defer.txt', optionflags=flags),
         doctest.DocFileSuite('format.txt', optionflags=flags),
         doctest.DocFileSuite('property.txt', optionflags=flags),