On 8/29/07, Panzerlurch <[EMAIL PROTECTED]> wrote:
>
> class Entry(Entity):
> has_field('title', Unicode(255), unique=True, required=True)
> has_and_belongs_to_many('tags', unique=True, of_kind='Tag',
> inverse='ideas')
>
> def __repr__(self):
> return '<Idea "%s">' % (self.title,)
>
> class Tag(Entity):
> has_field('tag', Unicode(50), unique=True, required=True)
> has_and_belongs_to_many('ideas', of_kind='Idea', inverse='tags')
>
> With the above code how can i assert that Tags can only be added once
> to an Entry?
>
> t = model.Tag(tag="test")
> t1 = model.Tag(tag="secret")
>
> model.entry.append(t)
> model.entry.appen(t1)
>
> now i would expect the following to cause an error or prevent it
> somehow:
> model.entry.append(t)
> because entry has Tag t already and it makes no sense to append it
> once more.
Well, to do what you describe at the table level, we'd need to set the
columns of the secondary table as primary_key. IMO, this should be
the default. And we could probably add the unique parameter you
describe to disable that behavior. Any thoughts? Want to try putting
together a patch for that?
Other than that, you could try playing with the new "collection_class"
argument, to have the relation behave as a set.
--
Gaëtan de Menten
http://openhex.org
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