Index: django/db/models/fields/related.py =================================================================== --- django/db/models/fields/related.py (revision 8090) +++ django/db/models/fields/related.py (working copy) @@ -23,7 +23,7 @@ pending_lookups = {} -def add_lazy_relation(cls, field, relation): +def add_lazy_relation(cls, field, relation, operation): """ Adds a lookup on ``cls`` when a related field is defined using a string, i.e.:: @@ -45,6 +45,8 @@ If the other model hasn't yet been loaded -- almost a given if you're using lazy relationships -- then the relation won't be set up until the class_prepared signal fires at the end of model initialization. + + operation is the work that must be performed once the relation can be resolved. """ # Check for recursive relations if relation == RECURSIVE_RELATIONSHIP_CONSTANT: @@ -66,11 +68,10 @@ # is prepared. model = get_model(app_label, model_name, False) if model: - field.rel.to = model - field.do_related_class(model, cls) + operation(field, model, cls) else: key = (app_label, model_name) - value = (cls, field) + value = (cls, field, operation) pending_lookups.setdefault(key, []).append(value) def do_pending_lookups(sender): @@ -78,9 +79,8 @@ Handle any pending relations to the sending model. Sent from class_prepared. """ key = (sender._meta.app_label, sender.__name__) - for cls, field in pending_lookups.pop(key, []): - field.rel.to = sender - field.do_related_class(sender, cls) + for cls, field, operation in pending_lookups.pop(key, []): + operation(field, sender, cls) dispatcher.connect(do_pending_lookups, signal=signals.class_prepared) @@ -108,7 +108,10 @@ other = self.rel.to if isinstance(other, basestring): - add_lazy_relation(cls, self, other) + def resolve_related_class(field, model, cls): + field.rel.to = model + field.do_related_class(model, cls) + add_lazy_relation(cls, self, other, resolve_related_class) else: self.do_related_class(other, cls) @@ -339,7 +342,7 @@ manager.clear() manager.add(*value) -def create_many_related_manager(superclass): +def create_many_related_manager(superclass, through=False): """Creates a manager that subclasses 'superclass' (which is a Manager) and adds behavior for many-to-many related objects.""" class ManyRelatedManager(superclass): @@ -353,6 +356,7 @@ self.join_table = join_table self.source_col_name = source_col_name self.target_col_name = target_col_name + self.through = through self._pk_val = self.instance._get_pk_val() if self._pk_val is None: raise ValueError("%r instance needs to have a primary key value before a many-to-many relationship can be used." % instance.__class__.__name__) @@ -360,21 +364,24 @@ def get_query_set(self): return superclass.get_query_set(self).filter(**(self.core_filters)) - def add(self, *objs): - self._add_items(self.source_col_name, self.target_col_name, *objs) + # If the ManyToMany relation has an intermediary model, + # the add and remove methods do not exist. + if through is None: + def add(self, *objs): + self._add_items(self.source_col_name, self.target_col_name, *objs) - # If this is a symmetrical m2m relation to self, add the mirror entry in the m2m table - if self.symmetrical: - self._add_items(self.target_col_name, self.source_col_name, *objs) - add.alters_data = True + # If this is a symmetrical m2m relation to self, add the mirror entry in the m2m table + if self.symmetrical: + self._add_items(self.target_col_name, self.source_col_name, *objs) + add.alters_data = True - def remove(self, *objs): - self._remove_items(self.source_col_name, self.target_col_name, *objs) + def remove(self, *objs): + self._remove_items(self.source_col_name, self.target_col_name, *objs) - # If this is a symmetrical m2m relation to self, remove the mirror entry in the m2m table - if self.symmetrical: - self._remove_items(self.target_col_name, self.source_col_name, *objs) - remove.alters_data = True + # If this is a symmetrical m2m relation to self, remove the mirror entry in the m2m table + if self.symmetrical: + self._remove_items(self.target_col_name, self.source_col_name, *objs) + remove.alters_data = True def clear(self): self._clear_items(self.source_col_name) @@ -385,6 +392,10 @@ clear.alters_data = True def create(self, **kwargs): + # This check needs to be done here, since we can't later remove this + # from the method lookup table, as we do with add and remove. + if through is not None: + raise AttributeError, "Cannot use create() on a ManyToManyField which specifies an intermediary model. Use %s's Manager instead." % through new_obj = self.model(**kwargs) new_obj.save() self.add(new_obj) @@ -472,7 +483,7 @@ # model's default manager. rel_model = self.related.model superclass = rel_model._default_manager.__class__ - RelatedManager = create_many_related_manager(superclass) + RelatedManager = create_many_related_manager(superclass, self.related.field.rel.through) qn = connection.ops.quote_name manager = RelatedManager( @@ -491,6 +502,10 @@ if instance is None: raise AttributeError, "Manager must be accessed via instance" + through = getattr(self.related.field.rel, 'through', None) + if through is not None: + raise AttributeError, "Cannot set values on a ManyToManyField which specifies an intermediary model. Use %s's Manager instead." % through + manager = self.__get__(instance) manager.clear() manager.add(*value) @@ -513,7 +528,7 @@ # model's default manager. rel_model=self.field.rel.to superclass = rel_model._default_manager.__class__ - RelatedManager = create_many_related_manager(superclass) + RelatedManager = create_many_related_manager(superclass, self.field.rel.through) qn = connection.ops.quote_name manager = RelatedManager( @@ -532,6 +547,10 @@ if instance is None: raise AttributeError, "Manager must be accessed via instance" + through = getattr(self.field.rel, 'through', None) + if through is not None: + raise AttributeError, "Cannot set values on a ManyToManyField which specifies an intermediary model. Use %s's Manager instead." % through + manager = self.__get__(instance) manager.clear() manager.add(*value) @@ -583,7 +602,7 @@ class ManyToManyRel(object): def __init__(self, to, num_in_admin=0, related_name=None, - limit_choices_to=None, symmetrical=True): + limit_choices_to=None, symmetrical=True, through=None): self.to = to self.num_in_admin = num_in_admin self.related_name = related_name @@ -593,7 +612,9 @@ self.edit_inline = False self.symmetrical = symmetrical self.multiple = True + self.through = through + class ForeignKey(RelatedField, Field): empty_strings_allowed = False def __init__(self, to, to_field=None, rel_class=ManyToOneRel, **kwargs): @@ -718,12 +739,21 @@ class ManyToManyField(RelatedField, Field): def __init__(self, to, **kwargs): kwargs['verbose_name'] = kwargs.get('verbose_name', None) + self.symmetrical_specified = kwargs.get('symmetrical', None) is not None kwargs['rel'] = ManyToManyRel(to, num_in_admin=kwargs.pop('num_in_admin', 0), related_name=kwargs.pop('related_name', None), limit_choices_to=kwargs.pop('limit_choices_to', None), - symmetrical=kwargs.pop('symmetrical', True)) + symmetrical=kwargs.pop('symmetrical', True), + through=kwargs.pop('through', None)) + self.db_table = kwargs.pop('db_table', None) + if kwargs['rel'].through is not None: + self.creates_table = False + assert self.db_table is None, "Cannot specify a db_table if an intermediary model is used." + else: + self.creates_table = True + Field.__init__(self, **kwargs) msg = ugettext_lazy('Hold down "Control", or "Command" on a Mac, to select more than one.') @@ -738,23 +768,44 @@ def _get_m2m_db_table(self, opts): "Function that can be curried to provide the m2m table name for this relation" - if self.db_table: + if self.rel.through is not None: + return self.rel.through_model._meta.db_table + elif self.db_table: return self.db_table else: return '%s_%s' % (opts.db_table, self.name) def _get_m2m_column_name(self, related): "Function that can be curried to provide the source column name for the m2m table" + if self.rel.through is not None: + for f in self.rel.through_model._meta.fields: + if hasattr(f,'rel') and f.rel and f.rel.to == related.model: + return f.column # If this is an m2m relation to self, avoid the inevitable name clash - if related.model == related.parent_model: + elif related.model == related.parent_model: return 'from_' + related.model._meta.object_name.lower() + '_id' else: return related.model._meta.object_name.lower() + '_id' def _get_m2m_reverse_name(self, related): "Function that can be curried to provide the related column name for the m2m table" + if self.rel.through is not None: + found = False + for f in self.rel.through_model._meta.fields: + if hasattr(f,'rel') and f.rel and f.rel.to == related.parent_model: + if related.model == related.parent_model: + # If this is an m2m-intermediate to self, + # the first foreign key you find will be + # the source column. Keep searching for + # the second foreign key. + if found: + return f.column + else: + found = True + else: + return f.column # If this is an m2m relation to self, avoid the inevitable name clash - if related.model == related.parent_model: + elif related.model == related.parent_model: return 'to_' + related.parent_model._meta.object_name.lower() + '_id' else: return related.parent_model._meta.object_name.lower() + '_id' @@ -797,7 +848,17 @@ # Set up the accessor for the m2m table name for the relation self.m2m_db_table = curry(self._get_m2m_db_table, cls._meta) - + + # Populate some necessary rel arguments so that cross-app relations + # work correctly. + if isinstance(self.rel.through, basestring): + def resolve_through_model(field, model, cls): + field.rel.through_model = model + add_lazy_relation(cls, self, self.rel.through, resolve_through_model) + elif self.rel.through: + self.rel.through_model = self.rel.through + self.rel.through = self.rel.through._meta.object_name + if isinstance(self.rel.to, basestring): target = self.rel.to else: Index: django/core/management/validation.py =================================================================== --- django/core/management/validation.py (revision 8090) +++ django/core/management/validation.py (working copy) @@ -102,6 +102,7 @@ if r.get_accessor_name() == rel_query_name: e.add(opts, "Reverse query name for field '%s' clashes with related field '%s.%s'. Add a related_name argument to the definition for '%s'." % (f.name, rel_opts.object_name, r.get_accessor_name(), f.name)) + seen_intermediary_signatures = [] for i, f in enumerate(opts.local_many_to_many): # Check to see if the related m2m field will clash with any # existing fields, m2m fields, m2m related objects or related @@ -112,7 +113,49 @@ # so skip the next section if isinstance(f.rel.to, (str, unicode)): continue - + if getattr(f.rel, 'through', None) is not None: + if hasattr(f.rel, 'through_model'): + if f.symmetrical_specified: + e.add(opts, "The symmetrical field has no meaning on m2m relations with intermediary models.") + from_model, to_model = cls, f.rel.to + seen_from, seen_to, seen_self = False, False, 0 + for inter_field in f.rel.through_model._meta.fields: + rel_to = getattr(inter_field.rel, 'to', None) + if from_model == to_model: + if rel_to == from_model: + seen_self += 1 + if seen_self > 2: + e.add(opts, "Intermediary model %s has more than two foreign keys through itself, which is ambiguous and is not permitted." % f.rel.through_model._meta.object_name) + else: + if rel_to == from_model: + if seen_from: + e.add(opts, "Intermediary model %s has more than one foreign key to one of its sides, %s, which is ambiguous and is not permitted." % (f.rel.through_model._meta.object_name, rel_from._meta.object_name)) + else: + seen_from = True + elif rel_to == to_model: + if seen_to: + e.add(opts, "Intermediary model %s has more than one foreign key to one of its sides, %s, which is ambiguous and is not permitted." % (f.rel.through_model._meta.object_name, rel_to._meta.object_name)) + else: + seen_to = True + if f.rel.through_model not in models.get_models(): + e.add(opts, "'%s' specifies an m2m relation through model %s, which has not been installed" % (f.name, f.rel.through)) + signature = (f.rel.to, cls, f.rel.through_model) + if signature in seen_intermediary_signatures: + e.add(opts, "The model %s has two manually-defined m2m relations through the model %s, which is not permitted. Please consider using an extra field on your intermediary model instead." % (cls._meta.object_name, f.rel.through_model._meta.object_name)) + else: + seen_intermediary_signatures.append(signature) + seen_related_fk, seen_this_fk = False, False + for field in f.rel.through_model._meta.fields: + if field.rel: + if not seen_related_fk and field.rel.to == f.rel.to: + seen_related_fk = True + elif field.rel.to == cls: + seen_this_fk = True + if not seen_related_fk or not seen_this_fk: + e.add(opts, "'%s' has a manually-defined m2m relation through model %s, which does not have foreign keys to %s and %s" % (f.name, f.rel.through, f.rel.to._meta.object_name, cls._meta.object_name)) + else: + e.add(opts, "'%s' specifies an m2m relation through model %s, which has not been installed" % (f.name, f.rel.through)) + rel_opts = f.rel.to._meta rel_name = RelatedObject(f.rel.to, cls, f).get_accessor_name() rel_query_name = f.related_query_name() Index: django/core/management/sql.py =================================================================== --- django/core/management/sql.py (revision 8090) +++ django/core/management/sql.py (working copy) @@ -353,7 +353,7 @@ qn = connection.ops.quote_name inline_references = connection.features.inline_fk_references for f in opts.local_many_to_many: - if not isinstance(f.rel, generic.GenericRel): + if f.creates_table: tablespace = f.db_tablespace or opts.db_tablespace if tablespace and connection.features.supports_tablespaces: tablespace_sql = ' ' + connection.ops.tablespace_sql(tablespace, inline=True) Index: django/contrib/admin/options.py =================================================================== --- django/contrib/admin/options.py (revision 8090) +++ django/contrib/admin/options.py (working copy) @@ -161,7 +161,10 @@ kwargs['empty_label'] = db_field.blank and _('None') or None else: if isinstance(db_field, models.ManyToManyField): - if db_field.name in self.raw_id_fields: + # If it uses an intermediary model, don't show field in admin. + if db_field.rel.through is not None: + return None + elif db_field.name in self.raw_id_fields: kwargs['widget'] = widgets.ManyToManyRawIdWidget(db_field.rel) kwargs['help_text'] = '' elif db_field.name in (list(self.filter_vertical) + list(self.filter_horizontal)): Index: django/contrib/contenttypes/generic.py =================================================================== --- django/contrib/contenttypes/generic.py (revision 8090) +++ django/contrib/contenttypes/generic.py (working copy) @@ -104,6 +104,9 @@ limit_choices_to=kwargs.pop('limit_choices_to', None), symmetrical=kwargs.pop('symmetrical', True)) + # By its very nature, a GenericRelation doesn't create a table. + self.creates_table = False + # Override content-type/object-id field names on the related class self.object_id_field_name = kwargs.pop("object_id_field", "object_id") self.content_type_field_name = kwargs.pop("content_type_field", "content_type") Index: tests/modeltests/invalid_models/models.py =================================================================== --- tests/modeltests/invalid_models/models.py (revision 8090) +++ tests/modeltests/invalid_models/models.py (working copy) @@ -110,7 +110,55 @@ class MissingRelations(models.Model): rel1 = models.ForeignKey("Rel1") rel2 = models.ManyToManyField("Rel2") + +class MissingManualM2MModel(models.Model): + name = models.CharField(max_length=5) + missing_m2m = models.ManyToManyField(Model, through="MissingM2MModel") + +class Person(models.Model): + name = models.CharField(max_length=5) +class Group(models.Model): + name = models.CharField(max_length=5) + primary = models.ManyToManyField(Person, through="Membership", related_name="primary") + secondary = models.ManyToManyField(Person, through="Membership", related_name="secondary") + tertiary = models.ManyToManyField(Person, through="RelationshipDoubleFK", related_name="tertiary") + +class GroupTwo(models.Model): + name = models.CharField(max_length=5) + primary = models.ManyToManyField(Person, through="Membership") + secondary = models.ManyToManyField(Group, through="MembershipMissingFK") + +class Membership(models.Model): + person = models.ForeignKey(Person) + group = models.ForeignKey(Group) + not_default_or_null = models.CharField(max_length=5) + +class MembershipMissingFK(models.Model): + person = models.ForeignKey(Person) + +class PersonSelfRefM2M(models.Model): + name = models.CharField(max_length=5) + friends = models.ManyToManyField('self', through="Relationship", symmetrical=True) + too_many_friends = models.ManyToManyField('self', through="RelationshipTripleFK") + +class Relationship(models.Model): + first = models.ForeignKey(PersonSelfRefM2M, related_name="rel_from_set") + second = models.ForeignKey(PersonSelfRefM2M, related_name="rel_to_set") + date_added = models.DateTimeField() + +class RelationshipTripleFK(models.Model): + first = models.ForeignKey(PersonSelfRefM2M, related_name="rel_from_set_2") + second = models.ForeignKey(PersonSelfRefM2M, related_name="rel_to_set_2") + third = models.ForeignKey(PersonSelfRefM2M, related_name="too_many_by_far") + date_added = models.DateTimeField() + +class RelationshipDoubleFK(models.Model): + first = models.ForeignKey(Person, related_name="first_related_name") + second = models.ForeignKey(Person, related_name="second_related_name") + third = models.ForeignKey(Group, related_name="rel_to_set") + date_added = models.DateTimeField() + model_errors = """invalid_models.fielderrors: "charfield": CharFields require a "max_length" attribute. invalid_models.fielderrors: "decimalfield": DecimalFields require a "decimal_places" attribute. invalid_models.fielderrors: "decimalfield": DecimalFields require a "max_digits" attribute. @@ -195,4 +243,11 @@ invalid_models.selfclashm2m: Reverse query name for m2m field 'm2m_4' clashes with field 'SelfClashM2M.selfclashm2m'. Add a related_name argument to the definition for 'm2m_4'. invalid_models.missingrelations: 'rel2' has m2m relation with model Rel2, which has not been installed invalid_models.missingrelations: 'rel1' has relation with model Rel1, which has not been installed +invalid_models.group: The model Group has two manually-defined m2m relations through the model Membership, which is not permitted. Please consider using an extra field on your intermediary model instead. +invalid_models.grouptwo: 'primary' has a manually-defined m2m relation through model Membership, which does not have foreign keys to Person and GroupTwo +invalid_models.grouptwo: 'secondary' has a manually-defined m2m relation through model MembershipMissingFK, which does not have foreign keys to Group and GroupTwo +invalid_models.missingmanualm2mmodel: 'missing_m2m' specifies an m2m relation through model MissingM2MModel, which has not been installed +invalid_models.group: Intermediary model RelationshipDoubleFK has more than one foreign key to one of its sides, Person, which is ambiguous and is not permitted. +invalid_models.personselfrefm2m: The symmetrical field has no meaning on m2m relations with intermediary models. +invalid_models.personselfrefm2m: Intermediary model RelationshipTripleFK has more than two foreign keys through itself, which is ambiguous and is not permitted. """ Index: tests/modeltests/m2m_through/__init__.py =================================================================== --- tests/modeltests/m2m_through/__init__.py (revision 0) +++ tests/modeltests/m2m_through/__init__.py (revision 0) @@ -0,0 +1 @@ + Index: tests/modeltests/m2m_through/models.py =================================================================== --- tests/modeltests/m2m_through/models.py (revision 0) +++ tests/modeltests/m2m_through/models.py (revision 0) @@ -0,0 +1,328 @@ +from django.db import models +from datetime import datetime + +# M2M described on one of the models +class Person(models.Model): + name = models.CharField(max_length=128) + + def __unicode__(self): + return self.name + +class Group(models.Model): + name = models.CharField(max_length=128) + members = models.ManyToManyField(Person, through='Membership') + custom_members = models.ManyToManyField(Person, through='CustomMembership', related_name="custom") + nodefaultsnonulls = models.ManyToManyField(Person, through='TestNoDefaultsOrNulls', related_name="testnodefaultsnonulls") + + def __unicode__(self): + return self.name + +class Membership(models.Model): + person = models.ForeignKey(Person) + group = models.ForeignKey(Group) + date_joined = models.DateTimeField(default=datetime.now) + invite_reason = models.CharField(max_length=64, null=True) + + def __unicode__(self): + return "%s is a member of %s" % (self.person.name, self.group.name) + +class CustomMembership(models.Model): + person = models.ForeignKey(Person, db_column="custom_person_column", related_name="custom_person_related_name") + group = models.ForeignKey(Group) + weird_fk = models.ForeignKey(Membership, null=True) + date_joined = models.DateTimeField(default=datetime.now) + + def __unicode__(self): + return "%s is a member of %s" % (self.person.name, self.group.name) + + class Meta: + db_table = "test_table" + +class TestNoDefaultsOrNulls(models.Model): + person = models.ForeignKey(Person) + group = models.ForeignKey(Group) + nodefaultnonull = models.CharField(max_length=5) + +class PersonSelfRefM2M(models.Model): + name = models.CharField(max_length=5) + friends = models.ManyToManyField('self', through="Friendship") + + def __unicode__(self): + return self.name + +class Friendship(models.Model): + first = models.ForeignKey(PersonSelfRefM2M, related_name="rel_from_set") + second = models.ForeignKey(PersonSelfRefM2M, related_name="rel_to_set") + date_friended = models.DateTimeField() + +__test__ = {'API_TESTS':""" +>>> from datetime import datetime + +### Creation and Saving Tests ### + +>>> bob = Person.objects.create(name='Bob') +>>> jim = Person.objects.create(name='Jim') +>>> jane = Person.objects.create(name='Jane') +>>> rock = Group.objects.create(name='Rock') +>>> roll = Group.objects.create(name='Roll') + +# We start out by making sure that the Group 'rock' has no members. +>>> rock.members.all() +[] + +# To make Jim a member of Group Rock, simply create a Membership object. +>>> m1 = Membership.objects.create(person=jim, group=rock) + +# We can do the same for Jane and Rock. +>>> m2 = Membership.objects.create(person=jane, group=rock) + +# Let's check to make sure that it worked. Jane and Jim should be members of Rock. +>>> rock.members.all() +[, ] + +# Now we can add a bunch more Membership objects to test with. +>>> m3 = Membership.objects.create(person=bob, group=roll) +>>> m4 = Membership.objects.create(person=jim, group=roll) +>>> m5 = Membership.objects.create(person=jane, group=roll) + +# We can get Jim's Group membership as with any ForeignKey. +>>> jim.group_set.all() +[, ] + +# Querying the intermediary model works like normal. +# In this case we get Jane's membership to Rock. +>>> m = Membership.objects.get(person=jane, group=rock) +>>> m + + +# Now we set some date_joined dates for further testing. +>>> m2.invite_reason = "She was just awesome." +>>> m2.date_joined = datetime(2006, 1, 1) +>>> m2.save() + +>>> m5.date_joined = datetime(2004, 1, 1) +>>> m5.save() + +>>> m3.date_joined = datetime(2004, 1, 1) +>>> m3.save() + +# It's not only get that works. Filter works like normal as well. +>>> Membership.objects.filter(person=jim) +[, ] + + +### Forward Descriptors Tests ### + +# Due to complications with adding via an intermediary model, +# the add method is not provided. +>>> rock.members.add(bob) +Traceback (most recent call last): +... +AttributeError: 'ManyRelatedManager' object has no attribute 'add' + +# Create is also disabled as it suffers from the same problems as add. +>>> rock.members.create(name='Anne') +Traceback (most recent call last): +... +AttributeError: Cannot use create() on a ManyToManyField which specifies an intermediary model. Use Membership's Manager instead. + +# Remove has similar complications, and is not provided either. +>>> rock.members.remove(jim) +Traceback (most recent call last): +... +AttributeError: 'ManyRelatedManager' object has no attribute 'remove' + +# Here we back up the list of all members of Rock. +>>> backup = list(rock.members.all()) + +# ...and we verify that it has worked. +>>> backup +[, ] + +# The clear function should still work. +>>> rock.members.clear() + +# Now there will be no members of Rock. +>>> rock.members.all() +[] + +# Assignment should not work with models specifying a through model for many of +# the same reasons as adding. +>>> rock.members = backup +Traceback (most recent call last): +... +AttributeError: Cannot set values on a ManyToManyField which specifies an intermediary model. Use Membership's Manager instead. + +# Let's re-save those instances that we've cleared. +>>> m1.save() +>>> m2.save() + +# Verifying that those instances were re-saved successfully. +>>> rock.members.all() +[, ] + + +### Reverse Descriptors Tests ### + +# Due to complications with adding via an intermediary model, +# the add method is not provided. +>>> bob.group_set.add(rock) +Traceback (most recent call last): +... +AttributeError: 'ManyRelatedManager' object has no attribute 'add' + +# Create is also disabled as it suffers from the same problems as add. +>>> bob.group_set.create(name='Funk') +Traceback (most recent call last): +... +AttributeError: Cannot use create() on a ManyToManyField which specifies an intermediary model. Use Membership's Manager instead. + +# Remove has similar complications, and is not provided either. +>>> jim.group_set.remove(rock) +Traceback (most recent call last): +... +AttributeError: 'ManyRelatedManager' object has no attribute 'remove' + +# Here we back up the list of all of Jim's groups. +>>> backup = list(jim.group_set.all()) +>>> backup +[, ] + +# The clear function should still work. +>>> jim.group_set.clear() + +# Now Jim will be in no groups. +>>> jim.group_set.all() +[] + +# Assignment should not work with models specifying a through model for many of +# the same reasons as adding. +>>> jim.group_set = backup +Traceback (most recent call last): +... +AttributeError: Cannot set values on a ManyToManyField which specifies an intermediary model. Use Membership's Manager instead. + +# Let's re-save those instances that we've cleared. +>>> m1.save() +>>> m4.save() + +# Verifying that those instances were re-saved successfully. +>>> jim.group_set.all() +[, ] + +### Custom Tests ### + +# Let's see if we can query through our second relationship. +>>> rock.custom_members.all() +[] + +# We can query in the opposite direction as well. +>>> bob.custom.all() +[] + +# Let's create some membership objects in this custom relationship. +>>> cm1 = CustomMembership.objects.create(person=bob, group=rock) +>>> cm2 = CustomMembership.objects.create(person=jim, group=rock) + +# If we get the number of people in Rock, it should be both Bob and Jim. +>>> rock.custom_members.all() +[, ] + +# Bob should only be in one custom group. +>>> bob.custom.all() +[] + +# Let's make sure our new descriptors don't conflict with the FK related_name. +>>> bob.custom_person_related_name.all() +[] + +### SELF-REFERENTIAL TESTS ### + +# Let's first create a person who has no friends. +>>> tony = PersonSelfRefM2M.objects.create(name="Tony") +>>> tony.friends.all() +[] + +# Now let's create another person for Tony to be friends with. +>>> chris = PersonSelfRefM2M.objects.create(name="Chris") +>>> f = Friendship.objects.create(first=tony, second=chris, date_friended=datetime.now()) + +# Tony should now show that Chris is his friend. +>>> tony.friends.all() +[] + +# But we haven't established that Chris is Tony's Friend. +>>> chris.friends.all() +[] + +# So let's do that now. +>>> f2 = Friendship.objects.create(first=chris, second=tony, date_friended=datetime.now()) + +# Having added Chris as a friend, let's make sure that his friend set reflects +# that addition. +>>> chris.friends.all() +[] + +# Chris gets mad and wants to get rid of all of his friends. +>>> chris.friends.clear() + +# Now he should not have any more friends. +>>> chris.friends.all() +[] + +# Since this is a symmetrical relation, Tony's friend link is deleted as well. +>>> tony.friends.all() +[] + + + +### QUERY TESTS ### + +# We can query for the related model by using its attribute name (members, in +# this case). +>>> Group.objects.filter(members__name='Bob') +[] + +# To query through the intermediary model, we specify its model name. +# In this case, membership. +>>> Group.objects.filter(membership__invite_reason="She was just awesome.") +[] + +# If we want to query in the reverse direction by the related model, use its +# model name (group, in this case). +>>> Person.objects.filter(group__name="Rock") +[, ] + +# If the m2m field has specified a related_name, using that will work. +>>> Person.objects.filter(custom__name="Rock") +[, ] + +# To query through the intermediary model in the reverse direction, we again +# specify its model name (membership, in this case). +>>> Person.objects.filter(membership__invite_reason="She was just awesome.") +[] + +# Let's see all of the groups that Jane joined after 1 Jan 2005: +>>> Group.objects.filter(membership__date_joined__gt=datetime(2005, 1, 1), membership__person =jane) +[] + +# Queries also work in the reverse direction: Now let's see all of the people +# that have joined Rock since 1 Jan 2005: +>>> Person.objects.filter(membership__date_joined__gt=datetime(2005, 1, 1), membership__group=rock) +[, ] + +# Conceivably, queries through membership could return correct, but non-unique +# querysets. To demonstrate this, we query for all people who have joined a +# group after 2004: +>>> Person.objects.filter(membership__date_joined__gt=datetime(2004, 1, 1)) +[, , ] + +# Jim showed up twice, because he joined two groups ('Rock', and 'Roll'): +>>> [(m.person.name, m.group.name) for m in +... Membership.objects.filter(date_joined__gt=datetime(2004, 1, 1))] +[(u'Jim', u'Rock'), (u'Jane', u'Rock'), (u'Jim', u'Roll')] + +# QuerySet's distinct() method can correct this problem. +>>> Person.objects.filter(membership__date_joined__gt=datetime(2004, 1, 1)).distinct() +[, ] +"""} \ No newline at end of file Index: tests/regressiontests/m2m_through_regress/__init__.py =================================================================== --- tests/regressiontests/m2m_through_regress/__init__.py (revision 0) +++ tests/regressiontests/m2m_through_regress/__init__.py (revision 0) @@ -0,0 +1 @@ + Index: tests/regressiontests/m2m_through_regress/models.py =================================================================== --- tests/regressiontests/m2m_through_regress/models.py (revision 0) +++ tests/regressiontests/m2m_through_regress/models.py (revision 0) @@ -0,0 +1,102 @@ +from django.db import models +from datetime import datetime +from django.contrib.auth.models import User + +# Forward declared intermediate model +class Membership(models.Model): + person = models.ForeignKey('Person') + group = models.ForeignKey('Group') + date_joined = models.DateTimeField(default=datetime.now) + + def __unicode__(self): + return "%s is a member of %s" % (self.person.name, self.group.name) + +class UserMembership(models.Model): + user = models.ForeignKey(User) + group = models.ForeignKey('Group') + date_joined = models.DateTimeField(default=datetime.now) + + def __unicode__(self): + return "%s is a user and member of %s" % (self.user.username, self.group.name) + +class Person(models.Model): + name = models.CharField(max_length=128) + + def __unicode__(self): + return self.name + +class Group(models.Model): + name = models.CharField(max_length=128) + # Membership object defined as a class + members = models.ManyToManyField(Person, through=Membership) + user_members = models.ManyToManyField(User, through='UserMembership') + + def __unicode__(self): + return self.name + +__test__ = {'API_TESTS':""" +# Create some dummy data +>>> bob = Person.objects.create(name='Bob') +>>> jim = Person.objects.create(name='Jim') + +>>> rock = Group.objects.create(name='Rock') +>>> roll = Group.objects.create(name='Roll') + +>>> frank = User.objects.create_user('frank','frank@example.com','password') +>>> jane = User.objects.create_user('jane','jane@example.com','password') + +# Now test that the forward declared Membership works +>>> Membership.objects.create(person=bob, group=rock) + + +>>> Membership.objects.create(person=bob, group=roll) + + +>>> Membership.objects.create(person=jim, group=rock) + + +>>> bob.group_set.all() +[, ] + +>>> roll.members.all() +[] + +# Error messages use the model name, not repr of the class name +>>> bob.group_set = [] +Traceback (most recent call last): +... +AttributeError: Cannot set values on a ManyToManyField which specifies an intermediary model. Use Membership's Manager instead. + +>>> roll.members = [] +Traceback (most recent call last): +... +AttributeError: Cannot set values on a ManyToManyField which specifies an intermediary model. Use Membership's Manager instead. + +>>> rock.members.create(name='Anne') +Traceback (most recent call last): +... +AttributeError: Cannot use create() on a ManyToManyField which specifies an intermediary model. Use Membership's Manager instead. + +>>> bob.group_set.create(name='Funk') +Traceback (most recent call last): +... +AttributeError: Cannot use create() on a ManyToManyField which specifies an intermediary model. Use Membership's Manager instead. + +# Now test that the intermediate with a relationship outside +# the current app (i.e., UserMembership) workds +>>> UserMembership.objects.create(user=frank, group=rock) + + +>>> UserMembership.objects.create(user=frank, group=roll) + + +>>> UserMembership.objects.create(user=jane, group=rock) + + +>>> frank.group_set.all() +[, ] + +>>> roll.user_members.all() +[] + +"""} \ No newline at end of file Index: AUTHORS =================================================================== --- AUTHORS (revision 8090) +++ AUTHORS (working copy) @@ -154,6 +154,7 @@ Maciej Fijalkowski Matthew Flanagan Eric Floehr + Eric Florenzano Vincent Foley Rudolph Froger Jorge Gajon Index: docs/model-api.txt =================================================================== --- docs/model-api.txt (revision 8090) +++ docs/model-api.txt (working copy) @@ -945,6 +945,112 @@ ======================= ============================================================ +Extra fields on many-to-many relationships +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +When you're only dealing with mixing and matching pizzas and toppings, a +standard ``ManyToManyField`` works great. However, sometimes you may want +to associate data with the relationship between two models. + +For example, consider the case of an application tracking the musical groups +which musicians belong to. There is a many-to-many relationship between a person +and the groups of which they are a member, so you could use a ManyToManyField +to represent this relationship. However, there is a lot of detail about the +membership that you might want to collect, such as the date at which the person +joined the group. + +For these situations, Django allows you to specify the model that will be used +to govern the many-to-many relationship. You can then put extra fields on the +intermediate model. The intermediate model is associated with the +``ManyToManyField`` by using the ``through`` argument to point to the model +that will act as an intermediary. For our musician example, the code would look +something like this:: + + class Person(models.Model): + # ... + name = models.CharField(max_length=128) + + def __unicode__(self): + return self.name + + class Group(models.Model): + # ... + name = models.CharField(max_length=128) + members = models.ManyToManyField(Person, through='Membership') + + def __unicode__(self): + return self.name + + class Membership(models.Model): + person = models.ForeignKey(Person) + group = models.ForeignKey(Group) + date_joined = models.DateField() + invite_reason = models.CharField(max_length=64) + +When you set up the intermediary model, you must explicitly specify foreign +keys to the models in ManyToMany relation. This explicit declaration makes +it clear how two models are related. + +Now that you have set up your ``ManyToManyField`` to use your intermediary +model (Membership, in this case), you're ready to use the convenience methods +provided by that ``ManyToManyField``. Here's an example of how you can query +for and use these models:: + + >>> ringo = Person.objects.create(name="Ringo Starr") + >>> paul = Person.objects.create(name="Paul McCartney") + >>> beatles = Group.objects.create(name="The Beatles") + >>> m1 = Membership.objects.create(person=ringo, group=beatles, + ... date_joined=date(1962, 8, 16), + ... invite_reason= "Needed a new drummer.") + >>> beatles.members.all() + [] + >>> ringo.group_set.all() + [] + >>> m2 = Membership.objects.create(person=paul, group=beatles, + ... date_joined=date(1960, 8, 1), + ... invite_reason= "Wanted to form a band.") + >>> beatles.members.all() + [, ] + +Unlike normal many-to-many fields, you *can't* use ``add``, ``create``, +or assignment (i.e., ``beatles.members = [...]``) to create relationships:: + + # THIS WILL NOT WORK + >>> beatles.members.add(john) + # NEITHER WILL THIS + >>> beatles.members.create(name="George Harrison") + # AND NEITHER WILL THIS + >>> beatles.members = [john, paul, ringo, george] + +Why? You can't just create a relationship between a Person and a Group - you +need to specify all the detail for the relationship required by the +Membership table. The simple ``add``, ``create`` and assignment calls +don't provide a way to specify this extra detail. As a result, they are +disabled for many-to-many relationships that use an intermediate model. +The only way to create a many-to-many relationship with an intermediate table +is to create instances of the intermediate model. + +The ``remove`` method is disabled for similar reasons. However, the +``clear()`` method can be used to remove all many-to-many relationships +for an instance:: + + # Beatles have broken up + >>> beatles.members.clear() + +Once you have established the many-to-many relationships by creating instances +of your intermediate model, you can issue queries. You can query using the +attributes of the many-to-many-related model:: + + # Find all the people in the Beatles whose name starts with 'Paul' + >>> beatles.objects.filter(person__name__startswith='Paul') + [] + +You can also query on the attributes of the intermediate model:: + + # Find all the members of the Beatles that joined after 1 Jan 1961 + >>> beatles.objects.filter(membership__date_joined__gt=date(1961,1,1)) + [