+class EntityProxyField(object):
+ descriptor_class = None
+
+ def __init__(self, *args, **kwargs):
+ if self.descriptor_class is None:
+ raise NotImplementedError('EntityProxyField subclasses must specify a descriptor_class.')
+ self.verbose_name = kwargs.get('verbose_name', None)
+ self.help_text = kwargs.get('help_text', None)
+
+ def actually_contribute_to_class(self, sender, **kwargs):
+ sender._entity_meta.add_proxy_field(self)
+ setattr(sender, self.attname, self.descriptor_class(self))
+
+ def contribute_to_class(self, cls, name):
+ if issubclass(cls, Entity):
+ self.name = name
+ self.attname = name
+ if self.verbose_name is None and name:
+ self.verbose_name = name.replace('_', ' ')
+ entity_class_prepared.connect(self.actually_contribute_to_class, sender=cls)
+ else:
+ raise FieldError('%s instances can only be declared on Entity subclasses.' % self.__class__.__name__)
+
+ def formfield(self, *args, **kwargs):
+ raise NotImplementedError('EntityProxyField subclasses must implement a formfield method.')
+
+ def value_from_object(self, obj):
+ return getattr(obj, self.attname)
+
+