On Aug 22, 2:12 am, Michael Bayer <mike...@zzzcomputing.com> wrote:
> On Aug 21, 2010, at 1:38 PM, Michael Bayer wrote:
>
> > On Aug 19, 2010, at 6:38 AM, Yap Sok Ann wrote:
>
> >> With declarative base, is it possible to use a relationship within a
> >> column_property?
>
> > you mean, as I am seeing below, to use the "any()" operator produced by a
> > relationship...
>
> >> Here's some sample code to illustrate what I want to
> >> achieve:
>
> >> players = relation('Player', back_populates='team')
>
> >> # This doesn't work
> >> #has_star_player = column_property(players.any(star=True))
>
> >> # This works
> >> has_star_player = column_property(
> >> exists().where(id == Player.team_id).where(Player.star ==
> >> True))
>
> >> # This also works
> >> Team.__mapper__.add_property(
> >> 'has_star_player2',
> >> column_property(Team.players.any(star=True)),
> >> )
>
> > so that's your answer - the two approaches you have are fine. For the
> > other one, you'd call players.comparator.any(), but that also doesn't work
> > since the relationship is not aware of its parent mapper at that point.
>
> oh well, lets make this easier, declarative documents this:
>
> Team.has_star_player_2 = column_property(Team.players.any(star=True))
>
Cool, that's definitely the best approach. Thank you.
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