Rails - Nov 2011 - I want to override ActiveModel#errors.as_json, but how?

Hey,

I want custom errors.as_json behavior from my implementation of
ActiveModel and with inheritance!

So how do I do something like shown in the following pseudo?

module A
   include ActiveModel

   def errors.to_json
      "blow"
   end
end

module B
    include A

   def errors.to_json
      "go " + super
   end
end


So far, I''ve been fooling around using instance_eval on errors in A,
but I can''t get inheritance from that in B.

Lille

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On Nov 16, 2:52 am, Lille
<lille.pengu...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> Hey,
>
> I want custom errors.as_json behavior from my implementation of
> ActiveModel and with inheritance!
>
> So how do I do something like shown in the following pseudo?
>
Ruby doesn''t work that way. You''d need to override to_json on
the
ActiveModel::Errors class. if you want to be able to have different
classes have an errors object that behave in different ways then you
could try subclassing ActiveModel::Errors and have the errors method
on your object return an instance of that subclass rather than an
instance of ActiveModel::Errors

Fred
> module A
>    include ActiveModel
>
>    def errors.to_json
>       "blow"
>    end
> end
>
> module B
>     include A
>
>    def errors.to_json
>       "go " + super
>    end
> end
>
> So far, I''ve been fooling around using instance_eval on errors in
A,
> but I can''t get inheritance from that in B.
>
> Lille
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On Nov 16, 8:30 am, Frederick Cheung
<frederick.che...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> On Nov 16, 2:52 am, Lille
<lille.pengu...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> Hey,
>
> > I want custom errors.as_json behavior from my implementation of
> > ActiveModel and with inheritance!
>
> > So how do I do something like shown in the following pseudo?
>
> Ruby doesn''t work that way. You''d need to override
to_json on the
> ActiveModel::Errors class. if you want to be able to have different
> classes have an errors object that behave in different ways then you
> could try subclassing ActiveModel::Errors and have the errors method
> on your object return an instance of that subclass rather than an
> instance of ActiveModel::Errors
>
yet another option would be to redefine the errors method to be

def errors
  super.tap {|e| e.extend ExtraErrorsBehaviour}
end

where ExtraErrorsBehaviour is a module that overrides some of the
methods on the errors object (I vaguely recall an railsconf talk a
long time ago by the jruby guys saying that calling extend forces ruby
to dump its method caches, i.e. calling extend a lot will slow you
down a bit but I''ve no idea if that applies to ruby 1.9.x)

Fred
>
>
>
> > module A
> >    include ActiveModel
>
> >    def errors.to_json
> >       "blow"
> >    end
> > end
>
> > module B
> >     include A
>
> >    def errors.to_json
> >       "go " + super
> >    end
> > end
>
> > So far, I''ve been fooling around using instance_eval on
errors in A,
> > but I can''t get inheritance from that in B.
>
> > Lille
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