models/fields.py

   1 from django.db import models
   2 from django import forms
   3 from django.core.exceptions import FieldError
   4 from django.utils.text import capfirst
   5 from philo.models.base import Entity
   6 from philo.signals import entity_class_prepared
   7
   8
   9 __all__ = ('AttributeField', 'RelationshipField')
  10
  11
  12 class EntityProxyField(object):
  13         descriptor_class = None
  14
  15         def __init__(self, *args, **kwargs):
  16                 if self.descriptor_class is None:
  17                         raise NotImplementedError('EntityProxyField subclasses must specify a descriptor_class.')
  18                 self.verbose_name = kwargs.get('verbose_name', None)
  19                 self.help_text = kwargs.get('help_text', None)
  20
  21         def actually_contribute_to_class(self, sender, **kwargs):
  22                 sender._entity_meta.add_proxy_field(self)
  23                 setattr(sender, self.attname, self.descriptor_class(self))
  24
  25         def contribute_to_class(self, cls, name):
  26                 if issubclass(cls, Entity):
  27                         self.name = name
  28                         self.attname = name
  29                         if self.verbose_name is None and name:
  30                                 self.verbose_name = name.replace('_', ' ')
  31                         entity_class_prepared.connect(self.actually_contribute_to_class, sender=cls)
  32                 else:
  33                         raise FieldError('%s instances can only be declared on Entity subclasses.' % self.__class__.__name__)
  34
  35         def formfield(self, *args, **kwargs):
  36                 raise NotImplementedError('EntityProxyField subclasses must implement a formfield method.')
  37
  38         def value_from_object(self, obj):
  39                 return getattr(obj, self.attname)
  40
  41
  42 class AttributeFieldDescriptor(object):
  43         def __init__(self, field):
  44                 self.field = field
  45
  46         def __get__(self, instance, owner):
  47                 if instance:
  48                         if self.field.key in instance._added_attribute_registry:
  49                                 return instance._added_attribute_registry[self.field.key]
  50                         if self.field.key in instance._removed_attribute_registry:
  51                                 return None
  52                         try:
  53                                 return instance.attributes[self.field.key]
  54                         except KeyError:
  55                                 return None
  56                 else:
  57                         raise AttributeError('The \'%s\' attribute can only be accessed from %s instances.' % (self.field.name, owner.__name__))
  58
  59         def __set__(self, instance, value):
  60                 if self.field.key in instance._removed_attribute_registry:
  61                         instance._removed_attribute_registry.remove(self.field.key)
  62                 instance._added_attribute_registry[self.field.key] = value
  63
  64         def __delete__(self, instance):
  65                 if self.field.key in instance._added_attribute_registry:
  66                         del instance._added_attribute_registry[self.field.key]
  67                 instance._removed_attribute_registry.append(self.field.key)
  68
  69
  70 class AttributeField(EntityProxyField):
  71         descriptor_class = AttributeFieldDescriptor
  72
  73         def __init__(self, key, field_template=None):
  74                 super(AttributeField, self).__init__()
  75                 self.key = key
  76                 if field_template is None:
  77                         field_template = models.CharField(max_length=255)
  78                 self.field_template = field_template
  79
  80         def formfield(self, **kwargs):
  81                 defaults = {'required': False, 'label': capfirst(self.verbose_name), 'help_text': self.help_text}
  82                 defaults.update(kwargs)
  83                 return self.field_template.formfield(**defaults)
  84
  85
  86 class RelationshipFieldDescriptor(object):
  87         def __init__(self, field):
  88                 self.field = field
  89
  90         def __get__(self, instance, owner):
  91                 if instance:
  92                         if self.field.key in instance._added_relationship_registry:
  93                                 return instance._added_relationship_registry[self.field.key]
  94                         if self.field.key in instance._removed_relationship_registry:
  95                                 return None
  96                         try:
  97                                 return instance.relationships[self.field.key]
  98                         except KeyError:
  99                                 return None
 100                 else:
 101                         raise AttributeError('The \'%s\' attribute can only be accessed from %s instances.' % (self.field.name, owner.__name__))
 102
 103         def __set__(self, instance, value):
 104                 if isinstance(value, (models.Model, type(None))):
 105                         if self.field.key in instance._removed_relationship_registry:
 106                                 instance._removed_relationship_registry.remove(self.field.key)
 107                         instance._added_relationship_registry[self.field.key] = value
 108                 else:
 109                         raise AttributeError('The \'%s\' attribute can only be set using existing Model objects.' % self.field.name)
 110
 111         def __delete__(self, instance):
 112                 if self.field.key in instance._added_relationship_registry:
 113                         del instance._added_relationship_registry[self.field.key]
 114                 instance._removed_relationship_registry.append(self.field.key)
 115
 116
 117 class RelationshipField(EntityProxyField):
 118         descriptor_class = RelationshipFieldDescriptor
 119
 120         def __init__(self, key, model, limit_choices_to=None):
 121                 super(RelationshipField, self).__init__()
 122                 self.key = key
 123                 self.model = model
 124                 if limit_choices_to is None:
 125                         limit_choices_to = {}
 126                 self.limit_choices_to = limit_choices_to
 127
 128         def formfield(self, form_class=forms.ModelChoiceField, **kwargs):
 129                 defaults = {'required': False, 'label': capfirst(self.verbose_name), 'help_text': self.help_text}
 130                 defaults.update(kwargs)
 131                 return form_class(self.model._default_manager.complex_filter(self.limit_choices_to), **defaults)
 132
 133         def value_from_object(self, obj):
 134                 relobj = super(RelationshipField, self).value_from_object(obj)
 135                 return getattr(relobj, 'pk', None)