added lazyvars package; relations renamed to relation

git-svn-id: svn://svn.cy55.de/Zope3/src/cybertools/trunk@631 fd906abe-77d9-0310-91a1-e0d9ade77398

lazyvars/README.txt

@@ -0,0 +1,72 @@
+Setting up and using LazyVars objects
+=====================================
+
+Lazy variables are only calculated when really needed, and they are
+calculated only once during the lifetime of the LazyVars objects they
+live in.
+
+This is especially useful when rendering web pages as during this
+rendering often the same data are used again and again, whereas you don't
+know at the beginning of the rendering process which data you will really
+need.
+
+We first need a function that will be used to provide a value
+for our lazy variable. This function will expect one parameter that will
+be set to the LazyVars object when the function is called.
+
+Our demonstration function will increment a counter on a context object
+(provided via the vars parameter) and return this counter so that we can easily
+follow the calls to the function:
+
+  >>> def getNumber(vars):
+  ...     context = vars.context
+  ...     context.counter += 1
+  ...     return context.counter
+
+We now register the function with our LazyVars class under the name we later
+want to use for accessing the variable:
+
+  >>> from cybertools.lazyvars.lazyvars import LazyVars
+  >>> LazyVars.registerVariable('number', getNumber)
+
+We also need a context object - that one which carries the above mentioned
+counter:
+
+  >>> class Number(object):
+  ...    counter = 0
+  >>> context = Number()
+
+This object is now used as the context parameter when creating a LazyVars
+object:
+  
+  >>> lv = LazyVars(context)
+
+So let's look if the LazyVars object can give us a value for the variable
+we have registered:
+
+  >>> lv.number
+  1
+
+The getNumber() function has been called that apparently has
+incremented the counter.
+
+What happens if we access the variable again?
+
+  >>> lv.number
+  1
+
+Same result, no incrementation, as it is now stored in the LazyVars object and
+retrieved without recalculation. Really lazy...
+
+We can even use the same function for more than one variable. When we first
+access the new variable the function is called again:
+
+  >>> LazyVars.registerVariable('number2', getNumber)
+  >>> lv.number2
+  2
+
+Our first variable is not affected by this:
+
+  >>> lv.number
+  1
+  

lazyvars/interfaces.py

@@ -0,0 +1,42 @@
+#
+#  Copyright (c) 2005 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
+#
+
+"""
+interface definitions for the LazyVars stuff.
+
+$Id$
+"""
+
+from zope.interface import Interface, Attribute
+
+
+class ILazyVars(Interface):
+    """ Generic adapter that provides lazy setting and returning
+        of variables.
+    """
+
+    def registerVariable(class_, name, function):
+        """ Class method: register a variable 'name' on class 'class_' that
+            will be provided by calling the function given.
+
+            The function should have one parameter that is set to the LazyVars
+            object when the function is called. Thus the method has access
+            to the instance variables (and other methods) of the LazyVars
+            object.
+        """
+

lazyvars/lazyvars.py

@@ -0,0 +1,47 @@
+#
+#  Copyright (c) 2005 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
+#
+
+"""
+Implementation of classes providing lazy variables.
+
+$Id$
+"""
+
+from zope.interface import implements
+import interfaces
+
+class LazyVars(object):
+    """ Basic adapter providing lazy variables.
+    """
+
+    implements(interfaces.ILazyVars)
+
+    variables = {}
+
+    def __init__(self, context):
+        self.context = context
+
+    @classmethod
+    def registerVariable(class_, name, method):
+        class_.variables[name] = method
+
+    def __getattr__(self, attr):
+        value = self.variables[attr](self)
+        setattr(self, attr, value)
+        return value
+    

lazyvars/tests.py

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+# $Id$
+
+import unittest
+from zope.testing.doctestunit import DocFileSuite
+from zope.app.testing import ztapi
+from zope.app import zapi
+from zope.interface.verify import verifyClass
+
+
+class TestMenu(unittest.TestCase):
+    "Test methods of the Menu class."
+
+    
+def test_suite():
+    return unittest.TestSuite((
+            DocFileSuite('README.txt'),
+            ))
+
+if __name__ == '__main__':
+    unittest.main(defaultTest='test_suite')

relation/__init__.py

@@ -0,0 +1,7 @@
+# -*- coding: UTF-8 -*-
+# -*- Mode: Python; py-indent-offset: 4 -*-
+# Copyright (C) 2005 Helmut Merz <helmutm@cy55.de>
+
+"""
+$Id$
+"""

relation/configure.zcml

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+<!-- $Id$ -->
+
+<configure
+   xmlns="http://namespaces.zope.org/zope"
+   i18n_domain="zope"
+   >
+
+  <!-- Security definitions -->
+
+  <!-- Content declarations -->
+
+  <utility provides=".interfaces.IRelationsRepository"
+           factory=".utilities.RelationsRepository" />
+
+  <utility provides=".interfaces.IRelationsRegistry"
+           factory=".utilities.RelationsRegistry" />
+
+  <!-- Register various browser related components, including all views -->
+  <!--include package=".browser" /-->
+
+</configure>