--- /dev/null
+"""
+The EntityProxyFields defined in this file can be assigned as fields on
+a subclass of philo.models.Entity. They act like any other model
+fields, but instead of saving their data to the database, they save it
+to attributes related to a model instance. Additionally, a new
+attribute will be created for an instance if and only if the field's
+value has been set. This is relevant i.e. for passthroughs, where the
+value of the field may be defined by some other instance's attributes.
+
+Example::
+
+ class Thing(Entity):
+ numbers = models.PositiveIntegerField()
+
+ class ThingProxy(Thing):
+ improvised = JSONAttribute(models.BooleanField)
+"""
+from itertools import tee
+from django import forms
+from django.core.exceptions import FieldError
+from django.db import models
+from django.db.models.fields import NOT_PROVIDED
+from django.utils.text import capfirst
+from philo.signals import entity_class_prepared
+from philo.models import ManyToManyValue, JSONValue, ForeignKeyValue, Attribute, Entity
+import datetime
+
+
+__all__ = ('JSONAttribute', 'ForeignKeyAttribute', 'ManyToManyAttribute')
+
+
+ATTRIBUTE_REGISTRY = '_attribute_registry'
+
+
+class EntityProxyField(object):
+ def __init__(self, verbose_name=None, help_text=None, default=NOT_PROVIDED, editable=True, choices=None, *args, **kwargs):
+ self.verbose_name = verbose_name
+ self.help_text = help_text
+ self.default = default
+ self.editable = editable
+ self._choices = choices or []
+
+ def actually_contribute_to_class(self, sender, **kwargs):
+ sender._entity_meta.add_proxy_field(self)
+
+ def contribute_to_class(self, cls, name):
+ if issubclass(cls, Entity):
+ self.name = self.attname = name
+ self.model = cls
+ 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, form_class=forms.CharField, **kwargs):
+ defaults = {
+ 'required': False,
+ 'label': capfirst(self.verbose_name),
+ 'help_text': self.help_text
+ }
+ if self.has_default():
+ defaults['initial'] = self.default
+ defaults.update(kwargs)
+ return form_class(**defaults)
+
+ def value_from_object(self, obj):
+ """The return value of this method will be used by the EntityForm as
+ this field's initial value."""
+ return getattr(obj, self.name)
+
+ def get_storage_value(self, value):
+ """Final conversion of `value` before it gets stored on an Entity instance.
+ This step is performed by the ProxyFieldForm."""
+ return value
+
+ def has_default(self):
+ return self.default is not NOT_PROVIDED
+
+ def _get_choices(self):
+ if hasattr(self._choices, 'next'):
+ choices, self._choices = tee(self._choices)
+ return choices
+ else:
+ return self._choices
+ choices = property(_get_choices)
+
+
+class AttributeFieldDescriptor(object):
+ def __init__(self, field):
+ self.field = field
+
+ def get_registry(self, instance):
+ if ATTRIBUTE_REGISTRY not in instance.__dict__:
+ instance.__dict__[ATTRIBUTE_REGISTRY] = {'added': set(), 'removed': set()}
+ return instance.__dict__[ATTRIBUTE_REGISTRY]
+
+ def __get__(self, instance, owner):
+ if instance is None:
+ return self
+
+ if self.field.name not in instance.__dict__:
+ instance.__dict__[self.field.name] = instance.attributes.get(self.field.attribute_key, None)
+
+ return instance.__dict__[self.field.name]
+
+ def __set__(self, instance, value):
+ if instance is None:
+ raise AttributeError("%s must be accessed via instance" % self.field.name)
+
+ self.field.validate_value(value)
+ instance.__dict__[self.field.name] = value
+
+ registry = self.get_registry(instance)
+ registry['added'].add(self.field)
+ registry['removed'].discard(self.field)
+
+ def __delete__(self, instance):
+ del instance.__dict__[self.field.name]
+
+ registry = self.get_registry(instance)
+ registry['added'].discard(self.field)
+ registry['removed'].add(self.field)
+
+
+def process_attribute_fields(sender, instance, created, **kwargs):
+ if ATTRIBUTE_REGISTRY in instance.__dict__:
+ registry = instance.__dict__[ATTRIBUTE_REGISTRY]
+ instance.attribute_set.filter(key__in=[field.attribute_key for field in registry['removed']]).delete()
+
+ for field in registry['added']:
+ try:
+ attribute = instance.attribute_set.get(key=field.attribute_key)
+ except Attribute.DoesNotExist:
+ attribute = Attribute()
+ attribute.entity = instance
+ attribute.key = field.attribute_key
+
+ value_class = field.value_class
+ if isinstance(attribute.value, value_class):
+ value = attribute.value
+ else:
+ if isinstance(attribute.value, models.Model):
+ attribute.value.delete()
+ value = value_class()
+
+ value.set_value(getattr(instance, field.name, None))
+ value.save()
+
+ attribute.value = value
+ attribute.save()
+ del instance.__dict__[ATTRIBUTE_REGISTRY]
+
+
+class AttributeField(EntityProxyField):
+ def __init__(self, attribute_key=None, **kwargs):
+ self.attribute_key = attribute_key
+ super(AttributeField, self).__init__(**kwargs)
+
+ def actually_contribute_to_class(self, sender, **kwargs):
+ super(AttributeField, self).actually_contribute_to_class(sender, **kwargs)
+ setattr(sender, self.name, AttributeFieldDescriptor(self))
+ opts = sender._entity_meta
+ if not hasattr(opts, '_has_attribute_fields'):
+ opts._has_attribute_fields = True
+ models.signals.post_save.connect(process_attribute_fields, sender=sender)
+
+ def contribute_to_class(self, cls, name):
+ if self.attribute_key is None:
+ self.attribute_key = name
+ super(AttributeField, self).contribute_to_class(cls, name)
+
+ def validate_value(self, value):
+ "Confirm that the value is valid or raise an appropriate error."
+ pass
+
+ @property
+ def value_class(self):
+ raise AttributeError("value_class must be defined on AttributeField subclasses.")
+
+
+class JSONAttribute(AttributeField):
+ value_class = JSONValue
+
+ def __init__(self, field_template=None, **kwargs):
+ super(JSONAttribute, self).__init__(**kwargs)
+ if field_template is None:
+ field_template = models.CharField(max_length=255)
+ self.field_template = field_template
+
+ def formfield(self, **kwargs):
+ defaults = {
+ 'required': False,
+ 'label': capfirst(self.verbose_name),
+ 'help_text': self.help_text
+ }
+ if self.has_default():
+ defaults['initial'] = self.default
+ defaults.update(kwargs)
+ return self.field_template.formfield(**defaults)
+
+ def value_from_object(self, obj):
+ value = super(JSONAttribute, self).value_from_object(obj)
+ if isinstance(self.field_template, (models.DateField, models.DateTimeField)):
+ value = self.field_template.to_python(value)
+ return value
+
+ def get_storage_value(self, value):
+ if isinstance(value, datetime.datetime):
+ return value.strftime("%Y-%m-%d %H:%M:%S")
+ if isinstance(value, datetime.date):
+ return value.strftime("%Y-%m-%d")
+ return value
+
+
+class ForeignKeyAttribute(AttributeField):
+ value_class = ForeignKeyValue
+
+ def __init__(self, model, limit_choices_to=None, **kwargs):
+ super(ForeignKeyAttribute, self).__init__(**kwargs)
+ self.to = model
+ if limit_choices_to is None:
+ limit_choices_to = {}
+ self.limit_choices_to = limit_choices_to
+
+ def validate_value(self, value):
+ if value is not None and not isinstance(value, self.to) :
+ raise TypeError("The '%s' attribute can only be set to an instance of %s or None." % (self.name, self.to.__name__))
+
+ def formfield(self, form_class=forms.ModelChoiceField, **kwargs):
+ defaults = {
+ 'queryset': self.to._default_manager.complex_filter(self.limit_choices_to)
+ }
+ defaults.update(kwargs)
+ return super(ForeignKeyAttribute, self).formfield(form_class=form_class, **defaults)
+
+ def value_from_object(self, obj):
+ relobj = super(ForeignKeyAttribute, self).value_from_object(obj)
+ return getattr(relobj, 'pk', None)
+
+ def get_related_field(self):
+ """Spoof being a rel from a ForeignKey."""
+ return self.to._meta.pk
+
+
+class ManyToManyAttribute(ForeignKeyAttribute):
+ value_class = ManyToManyValue
+
+ def validate_value(self, value):
+ if not isinstance(value, models.query.QuerySet) or value.model != self.to:
+ raise TypeError("The '%s' attribute can only be set to a %s QuerySet." % (self.name, self.to.__name__))
+
+ def formfield(self, form_class=forms.ModelMultipleChoiceField, **kwargs):
+ return super(ManyToManyAttribute, self).formfield(form_class=form_class, **kwargs)
+
+ def value_from_object(self, obj):
+ qs = super(ForeignKeyAttribute, self).value_from_object(obj)
+ try:
+ return qs.values_list('pk', flat=True)
+ except:
+ return []
\ No newline at end of file
git.ithinksw.org / philo.git / blobdiff