From: Anthony Eden <anthonyeden@...>
Date: 2009-05-16T05:13:02+09:00
Subject: Re: obj.attr(qualifier) = value -- possible?

On Fri, May 15, 2009 at 3:55 PM, Michael Schuerig <michael@schuerig.de> wrote:
> Joel VanderWerf wrote:
>
>> I'm pretty sure that's impossible -- there is no #() method, or #()=.
>> But there is #[]=, and you can adapt your Proxy approach to use it:
>
> That's a good suggestion, but unfortunately, it doesn't fit in my case.
> I'm trying to do this stuff in an extension module for a Rails has_many
> :through association. It looks roughly like this
>
> class Role < ActiveRecord::Base
>  validates_presence_of :type # actor, director, ...
> end
>
> class Movie < ActiveRecord::Base
>  has_many :roles
>  has_many :participants, :through => :roles do
>    def as(role)
>      self.scoped(...) # joins and conditions omitted
>    end
>  end
> end
>
> This allows me to write code like
>
> movie.participants.as('actor')
>
> On top of that, I'd like to be able to write
>
> movie.participants.as('actor') = params[:movie][:actors]
>
> and that's where I'm stuck.

If you're willing to use a block you could do

movie.participants.as('actor') { params[:movie][:actors] }

and then:

def as(role, &block)
  value = yield
end


-A


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