Hello list...
I wrote a couple of days ago about how to model an structure of three
classes
(http://groups.google.com/group/sqlalchemy/browse_thread/thread/5ba5c4ad16f789d6#).
I thing I almost have it, but I am still getting problems mapping an
structure like this.
class Child(rdb.Model):
def __init__(self):
self.field1 = “hello world”
class Parent(rdb.Model):
def __init__(self):
self.child1 = Child()
self.child2 = Child()
The “Parent” class has two different instances of a Child() class. I
am not even sure about how to treat this (two different 1:1
relationships or a 1:2 relationship).
My last try is this mapping:
(don't let the rdb.Model thing fool you, is just something that
automatically maps the class to the table specified in rdb.tablename).
class Child(rdb.Model):
rdb.metadata(metadata)
rdb.tablename("children_table")
id = Column("id", Integer, primary_key=True)
field1 = Column(“field1”, String(64)) #Irrelevant
def __init__(self):
self.field1 = “hello world”
class Parent(rdb.Model):
rdb.metadata(metadata)
rdb.tablename("parent_table”)
id = Column("id", Integer, primary_key=True)
child1_id = Column("child_1_id", Integer,
ForeignKey("children_table.id"))
child2_id = Column("child_2_id", Integer,
ForeignKey("children_table.id"))
child1 = relationship(Child,
primaryjoin = (child1_id=="children_table.id")
)
child2 = relationship(Child,
primaryjoin = (child2_id=="children_table.id")
)
I have tried (almost) everything. I say “almost” because obviously I
haven't tried the right thing. I keep getting errors that sqlalchemy
can't determine the relationship between the two tables.
It looks very similar to:
http://www.sqlalchemy.org/docs/orm/relationships.html#multiple-relationships-against-the-same-parent-child
but I also understand that maybe I can't get this working that way,
because I am actually putting two ForeignKeys from the same table
(“children_table”) in the parent table. I am not sure how that will
work out, or is correct or what... :-(
Thank you!
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