Re: [Sqlalchemy-users] ActiveMapper: many_to_many property binding failure?

Michael Bayer Sun, 06 Aug 2006 21:19:10 -0700

OK, well theres not too much of a bug here, except that when ActiveMapper has a circular relationship between two classes (comprised of more than one relationship(), that is), it fails to set up the relationships on either class. theres no immediate fix for this; while the compilation of plain (non-Active) mappers is able to handle a circular relationship like that, the way activemapper compiles on top of it is not quite as flexible. jonathan and i had talked about a way to add some extra string-based argument capabilities to Mapper/relation() so that a lot more of the compilation code in ActiveMapper could just be removed which would probably eliminate this issue.

however, the reason its not super-critical is because this relationship is a backref relationship, which means youre only supposed to set it up on one class, where "backref" handles the other direction:

class foo(activemapper.ActiveMapper):

class mapping:

name = column(String(30))

class baz(activemapper.ActiveMapper):

class mapping:

name = column(String(30))

foorel = many_to_many("foo", secondarytable, backref='bazrel')

additionally, i removed the extra "tometadata" call on "secondarytable" since its not needed, and also re-loaded foo1/baz1 after the session.clear() since it better tests the relatoinship and also foo1/baz1 cant be connected together outside of a session because theres a lazy loader on each that needs to be fired off (play around with it and youll see what i mean).

anyway, the working test added to activemapper.py in rev 1767...thanks for the convenient format.

On Aug 6, 2006, at 5:40 PM, Graham Higgins wrote:

class testmanytomany(testbase.PersistTest):

   def setUpAll(self):

   global secondarytable, foo, baz

   secondarytable = Table("secondarytable",

   activemapper.metadata,

   Column("foo_id", Integer, ForeignKey

("foo.id"),primary_key=True),

   Column("baz_id", Integer, ForeignKey

("baz.id"),primary_key=True))

   secondarytable.tometadata(activemapper.metadata)

   class foo(activemapper.ActiveMapper):

   class mapping:

   name = column(String(30))

   bazrel = many_to_many('baz', secondarytable,

backref='foorel')

   class baz(activemapper.ActiveMapper):

   class mapping:

   name = column(String(30))

   foorel = many_to_many("foo", secondarytable,

backref='bazrel')

   activemapper.metadata.connect(testbase.db)

   activemapper.create_tables()

   # Create a couple of activemapper objects

   def create_objects(self):

   return foo(name='foo1'), baz(name='baz1')

   def tearDownAll(self):

   clear_mappers()

   activemapper.drop_tables()

   def testbasic(self):

   # Set up activemapper objects

   foo1, baz1 = self.create_objects()

   objectstore.flush()

   objectstore.clear()

   # Just checking ...

   assert (foo1.name == 'foo1')

   assert (baz1.name == 'baz1')

   # Diagnostics ...

   # import sys

   # sys.stderr.write("\nbazrel missing from dir(foo1):\n%s\n"

% dir(foo1))

   # sys.stderr.write("\nbazrel in foo1 relations:\n%s\n" %

foo1.relations)

   # Optimistically based on activemapper one_to_many test, try

to append

   # baz1 to foo1.bazrel - (AttributeError: 'foo' object has no

attribute 'bazrel')

   foo1.bazrel.append(baz1)

   assert (foo1.bazrel == [baz1])

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Re: [Sqlalchemy-users] ActiveMapper: many_to_many property binding failure?

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