Haven't tried it, but have you considered switching the association
extension to a regular named_scope on Person? For simpler cases, I
know that the named_scope code is smart enough to use the scope
conditions to instantiate objects. Not sure if it will work here...
--Matt Jones
On May 11, 7:34 pm, Michael Schuerig <mich...@schuerig.de> wrote:
> I have a model layer containing Movie, Person, Role, and RoleType,
> making it possible to express facts such as "Clint Easterbunny is
> director of the movie Gran Milano".
>
> The relevant model and associations look like this
>
> class Movie < ActiveRecord::Base
> has_many :roles, :include => :role_type, :dependent => :destroy
>
> has_many :participants, :through => :roles, :source => :person do
> def as(role_name)
> self.scoped(
> :joins => 'CROSS JOIN role_types',
> :conditions => [
> "(roles.role_type_id = role_types.id) +
> " AND role_types.name = ?",
> role_name
> ]
> )
> end
> end
> ...
> end
>
> Querying is easy:
>
> m = Movie.find_by_title('Gran Milano')
> m.participants.as('director')
>
> However, changing relations is painful. It's already bad with has_many
> :through associations when the intermediate model is not completely
> dumb, and my scope trickery doesn't make it any better.
>
> Now, let's assume for a moment that participants was a plain has_many
> association. Then it would be possible to write things like
>
> m.participants.clear
> m.participants << Person.find_by_name('Steve McKing')
> m.participant_ids = params[:movie][:participants]
>
> With the given has_many :through, none of these work, as Role object
> won't validate without a role type. Anyway, what I would like to write
> is
>
> m.participants.as('actor').clear
> m.participants.as('actor') << Person.find_by_name('Steve McKing')
> m.participants.as('actor') = Person.find(params[:movie][:participants])
>
> I'm not sure this is possible with ActiveRecord as it is, but I'm
> looking forward to suggestions.
>
> Michael
>
> --
> Michael Schuerig
> mailto:mich...@schuerig.dehttp://www.schuerig.de/michael/
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