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Diffstat (limited to 'examples/poly_assoc/poly_assoc.py')
| -rw-r--r-- | examples/poly_assoc/poly_assoc.py | 48 |
1 files changed, 28 insertions, 20 deletions
diff --git a/examples/poly_assoc/poly_assoc.py b/examples/poly_assoc/poly_assoc.py index ecdc403e7..1854bfa3d 100644 --- a/examples/poly_assoc/poly_assoc.py +++ b/examples/poly_assoc/poly_assoc.py @@ -1,28 +1,29 @@ """ "polymorphic" associations, ala ActiveRecord. -In this example, we are specifically targeting this ActiveRecord functionality: +In this example, we are specifically targeting this ActiveRecord +functionality: http://wiki.rubyonrails.org/rails/pages/UnderstandingPolymorphicAssociations -The term "polymorphic" here means "object X can be referenced by objects A, B, and C, -along a common line of association". +The term "polymorphic" here means "object X can be referenced by objects A, B, +and C, along a common line of association". -In this example we illustrate the relationship in both directions. -A little bit of property magic is used to smooth the edges. +In this example we illustrate the relationship in both directions. A little +bit of property magic is used to smooth the edges. -AR creates this relationship in such a way that disallows -any foreign key constraint from existing on the association. -For a different way of doing this, see -poly_assoc_fks.py. The interface is the same, the efficiency is more or less the same, -but foreign key constraints may be used. That example also better separates -the associated target object from those which associate with it. +AR creates this relationship in such a way that disallows any foreign key +constraint from existing on the association. For a different way of doing +this, see poly_assoc_fks.py. The interface is the same, the efficiency is more +or less the same, but foreign key constraints may be used. That example also +better separates the associated target object from those which associate with +it. """ from sqlalchemy import MetaData, Table, Column, Integer, String, and_ -from sqlalchemy.orm import (mapper, relationship, create_session, class_mapper, - backref) +from sqlalchemy.orm import mapper, relationship, sessionmaker, \ + class_mapper, backref metadata = MetaData('sqlite://') @@ -41,12 +42,15 @@ addresses = Table("addresses", metadata, class Address(object): def __init__(self, type): self.addressable_type = type - member = property(lambda self: getattr(self, '_backref_%s' % self.addressable_type)) + @property + def member(self): + return getattr(self, '_backref_%s' % self.addressable_type) def addressable(cls, name, uselist=True): """addressable 'interface'. - if you really wanted to make a "generic" version of this function, it's straightforward. + if you really wanted to make a "generic" version of this function, it's + straightforward. """ # create_address function, imitaes the rails example. @@ -71,8 +75,13 @@ def addressable(cls, name, uselist=True): foreign_keys = [addresses.c.addressable_id] mapper.add_property(name, relationship( Address, - primaryjoin=primaryjoin, uselist=uselist, foreign_keys=foreign_keys, - backref=backref('_backref_%s' % table.name, primaryjoin=list(table.primary_key)[0] == addresses.c.addressable_id, foreign_keys=foreign_keys) + primaryjoin=primaryjoin, + uselist=uselist, + foreign_keys=foreign_keys, + backref=backref('_backref_%s' % table.name, + primaryjoin=list(table.primary_key)[0] ==\ + addresses.c.addressable_id, + foreign_keys=foreign_keys) ) ) @@ -124,12 +133,11 @@ a2.street = '345 orchard ave' a3 = o1.create_address() a3.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 |