##############################################################################
#
# Copyright (c) 2002 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.
#
##############################################################################
"""Computed attributes based on schema fields
"""
from copy import copy
import sys
import zope.schema
from zope import interface
from zope import event
from zope.schema import interfaces
from zope.schema._bootstrapinterfaces import NO_VALUE
_marker = object()
@interface.implementer(interfaces.IFieldUpdatedEvent)
class FieldUpdatedEvent(object):
def __init__(self, inst, field, old_value, new_value):
self.inst = inst
self.field = field
self.old_value = old_value
self.new_value = new_value
class FieldProperty(object):
"""Computed attributes based on schema fields
Field properties provide default values, data validation and error messages
based on data found in field meta-data.
Note that FieldProperties cannot be used with slots. They can only
be used for attributes stored in instance dictionaries.
"""
def __init__(self, field, name=None):
if name is None:
name = field.__name__
self.__field = field
self.__name = name
def __get__(self, inst, klass):
if inst is None:
return self
value = inst.__dict__.get(self.__name, _marker)
if value is _marker:
field = self.__field.bind(inst)
value = getattr(field, 'default', _marker)
if value is _marker:
raise AttributeError(self.__name)
return value
def queryValue(self, inst, default):
value = inst.__dict__.get(self.__name, default)
if value is default:
field = self.__field.bind(inst)
value = getattr(field, 'default', default)
return value
def __set__(self, inst, value):
field = self.__field.bind(inst)
field.validate(value)
if field.readonly and self.__name in inst.__dict__:
raise ValueError(self.__name, 'field is readonly')
oldvalue = self.queryValue(inst, NO_VALUE)
inst.__dict__[self.__name] = value
event.notify(FieldUpdatedEvent(inst, field, oldvalue, value))
def __getattr__(self, name):
return getattr(self.__field, name)
def createFieldProperties(schema, omit=[]):
"""For each fields in `schema` create a FieldProperty on the class.
schema ... interface those fields should be added to class
omit ... list of field names to be omitted in creation
Usage::
class A(object):
zope.schema.fieldproperty.createFieldProperties(IMySchema)
"""
frame = sys._getframe(1)
for name in zope.schema.getFieldNamesInOrder(schema):
if name in omit:
continue
frame.f_locals[name] = FieldProperty(schema[name])
class FieldPropertyStoredThroughField(object):
def __init__(self, field, name=None):
if name is None:
name = field.__name__
self.field = copy(field)
self.field.__name__ = "__st_%s_st" % self.field.__name__
self.__name = name
def setValue(self, inst, field, value):
field.set(inst, value)
def getValue(self, inst, field):
return field.query(inst, _marker)
def queryValue(self, inst, field, default):
return field.query(inst, default)
def __getattr__(self, name):
return getattr(self.field, name)
def __get__(self, inst, klass):
if inst is None:
return self
field = self.field.bind(inst)
value = self.getValue(inst, field)
if value is _marker:
value = getattr(field, 'default', _marker)
if value is _marker:
raise AttributeError(self.__name)
return value
def __set__(self, inst, value):
field = self.field.bind(inst)
field.validate(value)
if field.readonly:
if self.queryValue(inst, field, _marker) is _marker:
field.readonly = False
self.setValue(inst, field, value)
field.readonly = True
return
else:
raise ValueError(self.__name, 'field is readonly')
oldvalue = self.queryValue(inst, field, NO_VALUE)
self.setValue(inst, field, value)
event.notify(FieldUpdatedEvent(inst, self.field, oldvalue, value))