diff options
Diffstat (limited to 'examples/poly_assoc/poly_assoc_fk.py')
| -rw-r--r-- | examples/poly_assoc/poly_assoc_fk.py | 59 |
1 files changed, 33 insertions, 26 deletions
diff --git a/examples/poly_assoc/poly_assoc_fk.py b/examples/poly_assoc/poly_assoc_fk.py index 96c9935c3..a22020e08 100644 --- a/examples/poly_assoc/poly_assoc_fk.py +++ b/examples/poly_assoc/poly_assoc_fk.py @@ -1,26 +1,26 @@ """ "polymorphic" associations, ala SQLAlchemy. -See "poly_assoc.py" for an imitation of this functionality as implemented -in ActiveRecord. - -Here, we build off the previous example, adding an association table -that allows the relationship to be expressed as a many-to-one from the -"model" object to its "association", so that each model table bears the foreign -key constraint. This allows the same functionality via traditional -normalized form with full constraints. It also isolates the target -associated object from its method of being associated, allowing greater -flexibility in its usage. - -As in the previous example, a little bit of property magic is used -to smooth the edges. - -For a more genericized version of this example, see -poly_assoc_generic.py. +See "poly_assoc.py" for an imitation of this functionality as implemented in +ActiveRecord. + +Here, we build off the previous example, adding an association table that +allows the relationship to be expressed as a many-to-one from the "model" +object to its "association", so that each model table bears the foreign key +constraint. This allows the same functionality via traditional normalized form +with full constraints. It also isolates the target associated object from its +method of being associated, allowing greater flexibility in its usage. + +As in the previous example, a little bit of property magic is used to smooth +the edges. + +For a more genericized version of this example, see poly_assoc_generic.py. """ -from sqlalchemy import MetaData, Table, Column, Integer, String, ForeignKey -from sqlalchemy.orm import mapper, relationship, create_session, class_mapper +from sqlalchemy import MetaData, Table, Column, Integer, String, \ + ForeignKey +from sqlalchemy.orm import mapper, relationship, sessionmaker, \ + class_mapper metadata = MetaData('sqlite://') @@ -42,7 +42,11 @@ address_associations = Table("address_associations", metadata, ) class Address(object): - member = property(lambda self: getattr(self.association, '_backref_%s' % self.association.type)) + + @property + def member(self): + return getattr(self.association, '_backref_%s' + % self.association.type) class AddressAssoc(object): def __init__(self, name): @@ -56,7 +60,10 @@ def addressable(cls, name, uselist=True): """ mapper = class_mapper(cls) table = mapper.local_table - mapper.add_property('address_rel', relationship(AddressAssoc, backref='_backref_%s' % table.name)) + mapper.add_property('address_rel', + relationship(AddressAssoc, + backref='_backref_%s' % table.name) + ) if uselist: # list based property decorator @@ -88,7 +95,7 @@ users = Table("users", metadata, Column('id', Integer, primary_key=True), Column('name', String(50), nullable=False), # this column ties the users table into the address association - Column('assoc_id', None, ForeignKey('address_associations.assoc_id')) + Column('assoc_id', Integer, ForeignKey('address_associations.assoc_id')) ) class User(object): @@ -104,7 +111,7 @@ orders = Table("orders", metadata, Column('id', Integer, primary_key=True), Column('description', String(50), nullable=False), # this column ties the orders table into the address association - Column('assoc_id', None, ForeignKey('address_associations.assoc_id')) + Column('assoc_id', Integer, ForeignKey('address_associations.assoc_id')) ) class Order(object): @@ -136,17 +143,17 @@ a2.street = '345 orchard ave' o1.address = Address() o1.address.street = '444 park ave.' -sess = create_session() +sess = sessionmaker()() sess.add(u1) sess.add(o1) -sess.flush() -sess.expunge_all() +sess.commit() # query objects, get their addresses bob = sess.query(User).filter_by(name='bob').one() -assert [s.street for s in bob.addresses] == ['123 anywhere street', '345 orchard ave'] +assert [s.street for s in bob.addresses] == \ + ['123 anywhere street', '345 orchard ave'] order = sess.query(Order).filter_by(description='order 1').one() assert order.address.street == '444 park ave.' |