Added printing requirements

zope/schema/accessors.py

@@ -0,0 +1,120 @@
+##############################################################################
+#
+# Copyright (c) 2003 Zope Foundation and Contributors.
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+##############################################################################
+"""
+Field accessors
+===============
+
+Accessors are used to model methods used to access data defined by fields.
+Accessors are fields that work by decorating existing fields.
+
+To define accessors in an interface, use the accessors function::
+
+  class IMyInterface(Interface):
+
+     getFoo, setFoo = accessors(Text(title=u'Foo', ...))
+
+     getBar = accessors(TextLine(title=u'Foo', readonly=True, ...)
+
+
+Normally a read accessor and a write accessor are defined.  Only a
+read accessor is defined for read-only fields.
+
+Read accessors function as access method specifications and as field
+specifications.  Write accessors are solely method specifications.
+"""
+
+from zope.interface import providedBy, implementedBy
+from zope.interface.interface import Method
+
+
+class FieldReadAccessor(Method):
+    """Field read accessor
+    """
+
+    # A read field accessor is a method and a field.
+    # A read accessor is a decorator of a field, using the given
+    # fields properties to provide meta data.
+
+    def __provides__(self):
+        return providedBy(self.field) + implementedBy(FieldReadAccessor)
+    __provides__ = property(__provides__)
+
+    def __init__(self, field):
+        self.field = field
+        Method.__init__(self, '')
+        self.__doc__ = 'get %s' % field.__doc__
+
+    def getSignatureString(self):
+        return '()'
+
+    def getSignatureInfo(self):
+        return {'positional': (),
+                'required': (),
+                'optional': (),
+                'varargs': None,
+                'kwargs': None,
+                }
+
+    def get(self, object):
+        return getattr(object, self.__name__)()
+
+    def query(self, object, default=None):
+        try:
+            f = getattr(object, self.__name__)
+        except AttributeError:
+            return default
+        else:
+            return f()
+
+    def set(self, object, value):
+        if self.readonly:
+            raise TypeError("Can't set values on read-only fields")
+        getattr(object, self.writer.__name__)(value)
+
+    def __getattr__(self, name):
+        return getattr(self.field, name)
+
+    def bind(self, object):
+        clone = self.__class__.__new__(self.__class__)
+        clone.__dict__.update(self.__dict__)
+        clone.field = self.field.bind(object)
+        return clone
+
+
+class FieldWriteAccessor(Method):
+
+    def __init__(self, field):
+        Method.__init__(self, '')
+        self.field = field
+        self.__doc__ = 'set %s' % field.__doc__
+
+    def getSignatureString(self):
+        return '(newvalue)'
+
+    def getSignatureInfo(self):
+        return {'positional': ('newvalue',),
+                'required': ('newvalue',),
+                'optional': (),
+                'varargs': None,
+                'kwargs': None,
+                }
+
+
+def accessors(field):
+    reader = FieldReadAccessor(field)
+    yield reader
+    if not field.readonly:
+        writer = FieldWriteAccessor(field)
+        reader.writer = writer
+        yield writer