On Jan 4, 2011, at 2:34 PM, Martijn Moeling wrote:
> Michael,
>
> Thank you,
>
> reading trough your example (and running it)
> made me understand a bit more how SQLA works.
> I managed to get it all working,
>
> Since I was on my way to something a bit slightly more complex ...one last
> Question
>
> What if I would like to:
>
> Class RelationType(Base):
> __tablename__ = 'relationtypes'
> Id = Column(Integer,
> primary_key=True)
> ChildRelationType = Column(Unicode(20))
> ParentRelationType = Column(Unicode(20))
>
> Some data for information:
>
> Id ChildRelationType
> ParentRelationType
> 1 "Parent"
> "Child"
> 2 "Supplier"
> "Customer"
>
> I will put additional logic to print Mother - Son, in Fact this is not really
> what I am doing but I feel the need to make it a bit more understandable for
> the MailingList
> At the end it will be something with molecules, not really interesting and
> easy to understand.
>
>
>
>>
>> relation_table = Table('relation', Base.metadata,
>> Column('rid', Integer, ForeignKey('affiliations.id'), primary_key=True),
> Column('RelationType', integer, ForeignKey('relationtypes.Id')),
>> Column('lid', Integer, ForeignKey('affiliations.id'), primary_key=True),
>> )
>
>
> Adding this column to the relation_table does not make a difference but....
>
> Somehow I need to get a reference to the "type of relation"
> Setting the relation_type MUST be done whilst "Appending" it. i.e. every
> relation between "Affiliates" must have a reason
>
>
> Is this possible or is there another way to do such a thing, I feel logically
> it should be part of the relation_table.
>
> Thank you Again for your great help. I'm Not really good in Database stuff,
> but did/do a lot on the mod_python/mod_wsgi lists so I know about the huge
> amounts of time spent....
You then turn the relation_table into an association object. A declarative
example is in
http://www.sqlalchemy.org/docs/orm/relationships.html#association-object .
The "Relation" class will have a relationship() to "child", or similar (and
probably "parent" as a backref). Intercept the "set" event on this
attribute(s) and use that to establish the desired "RelationType" value. This
interception can be done with the @validates decorator:
http://www.sqlalchemy.org/docs/orm/mapper_config.html#simple-validators .
--
You received this message because you are subscribed to the Google Groups
"sqlalchemy" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/sqlalchemy?hl=en.
