ms wrote:> Hey,
>
> thanks for reading this post. How do you handle dependencies? A really
> simple example: I''ve got a table called "entity" and
another table,
> let''s say, "entity_type". The entity types can be
changed, of course,
> they also should be deletable, but only, if they are not used by some
> entities! How can I ensure this in Rails or directly in the DBMS
> (postgres)?
You need foreign key constraints in the database; check the Postgres
docs for more details. I would *highly* recommend using the
foreign_key_migrations plugin, which will manage these constraints
automatically from your migrations (it''s at
http://github.com/harukizaemon , along with a lot of other good stuff).
Big tip: always make your constraints deferrable. It will make testing
*much* easier.
> Do I have to check it manually within a validate-method in
> the model?
I suppose you could, but the DB will already do that if you have the
constraints.
Best,
--
Marnen Laibow-Koser
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
http://www.marnen.org
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