models/fields.py

   1 from django.db import models
   2 from django import forms
   3 from django.core.exceptions import FieldError
   4 from philo.models.base import Entity
   5 from philo.signals import entity_class_prepared
   6
   7
   8 __all__ = ('AttributeField', 'RelationshipField')
   9
  10
  11 class EntityProxyField(object):
  12         descriptor_class = None
  13
  14         def __init__(self, *args, **kwargs):
  15                 if self.descriptor_class is None:
  16                         raise NotImplementedError('EntityProxyField subclasses must specify a descriptor_class.')
  17
  18         def actually_contribute_to_class(self, sender, **kwargs):
  19                 sender._entity_meta.add_proxy_field(self)
  20                 setattr(sender, self.attname, self.descriptor_class(self))
  21
  22         def contribute_to_class(self, cls, name):
  23                 if issubclass(cls, Entity):
  24                         self.name = name
  25                         self.attname = name
  26                         entity_class_prepared.connect(self.actually_contribute_to_class, sender=cls)
  27                 else:
  28                         raise FieldError('%s instances can only be declared on Entity subclasses.' % self.__class__.__name__)
  29
  30         def formfield(self, *args, **kwargs):
  31                 raise NotImplementedError('EntityProxyField subclasses must implement a formfield method.')
  32
  33         def value_from_object(self, obj):
  34                 return getattr(obj, self.attname)
  35
  36
  37 class AttributeFieldDescriptor(object):
  38         def __init__(self, field):
  39                 self.field = field
  40
  41         def __get__(self, instance, owner):
  42                 if instance:
  43                         if self.field.key in instance._added_attribute_registry:
  44                                 return instance._added_attribute_registry[self.field.key]
  45                         if self.field.key in instance._removed_attribute_registry:
  46                                 return None
  47                         try:
  48                                 return instance.attributes[self.field.key]
  49                         except KeyError:
  50                                 return None
  51                 else:
  52                         raise AttributeError('The \'%s\' attribute can only be accessed from %s instances.' % (self.field.name, owner.__name__))
  53
  54         def __set__(self, instance, value):
  55                 if self.field.key in instance._removed_attribute_registry:
  56                         instance._removed_attribute_registry.remove(self.field.key)
  57                 instance._added_attribute_registry[self.field.key] = value
  58
  59         def __delete__(self, instance):
  60                 if self.field.key in instance._added_attribute_registry:
  61                         del instance._added_attribute_registry[self.field.key]
  62                 instance._removed_attribute_registry.append(self.field.key)
  63
  64
  65 class AttributeField(EntityProxyField):
  66         descriptor_class = AttributeFieldDescriptor
  67
  68         def __init__(self, key, field_template=None):
  69                 self.key = key
  70                 if field_template is None:
  71                         field_template = models.CharField(max_length=255)
  72                 self.field_template = field_template
  73
  74         def formfield(self, *args, **kwargs):
  75                 field = self.field_template.formfield(*args, **kwargs)
  76                 field.required = False
  77                 return field
  78
  79
  80 class RelationshipFieldDescriptor(object):
  81         def __init__(self, field):
  82                 self.field = field
  83
  84         def __get__(self, instance, owner):
  85                 if instance:
  86                         if self.field.key in instance._added_relationship_registry:
  87                                 return instance._added_relationship_registry[self.field.key]
  88                         if self.field.key in instance._removed_relationship_registry:
  89                                 return None
  90                         try:
  91                                 return instance.relationships[self.field.key]
  92                         except KeyError:
  93                                 return None
  94                 else:
  95                         raise AttributeError('The \'%s\' attribute can only be accessed from %s instances.' % (self.field.name, owner.__name__))
  96
  97         def __set__(self, instance, value):
  98                 if isinstance(value, (models.Model, type(None))):
  99                         if self.field.key in instance._removed_relationship_registry:
 100                                 instance._removed_relationship_registry.remove(self.field.key)
 101                         instance._added_relationship_registry[self.field.key] = value
 102                 else:
 103                         raise AttributeError('The \'%s\' attribute can only be set using existing Model objects.' % self.field.name)
 104
 105         def __delete__(self, instance):
 106                 if self.field.key in instance._added_relationship_registry:
 107                         del instance._added_relationship_registry[self.field.key]
 108                 instance._removed_relationship_registry.append(self.field.key)
 109
 110
 111 class RelationshipField(EntityProxyField):
 112         descriptor_class = RelationshipFieldDescriptor
 113
 114         def __init__(self, key, model, limit_choices_to=None):
 115                 self.key = key
 116                 self.model = model
 117                 if limit_choices_to is None:
 118                         limit_choices_to = {}
 119                 self.limit_choices_to = limit_choices_to
 120
 121         def formfield(self, form_class=forms.ModelChoiceField, **kwargs):
 122                 field = form_class(self.model._default_manager.complex_filter(self.limit_choices_to), **kwargs)
 123                 field.required = False
 124                 return field
 125
 126         def value_from_object(self, obj):
 127                 relobj = super(RelationshipField, self).value_from_object(obj)
 128                 return getattr(relobj, 'pk', None)