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