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))
>
>
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