From: "Jean-François Trân" <jftran@...>
Date: 2007-11-24T04:59:52+09:00
Subject: Re: Developing Rails plugin: need some metaprog. help

Hi Joshua,

> I'm developing an authorization plugin that looks like the
> following so far:
>
> module Incense
>   module Authorization
>     def self.included(base_class)
>       base_class.extend(ClassMethods)
>     end
>
>     module ClassMethods
>       def performs_authorization(options = {})
>         before_filter :prepare_user
>
>         include(InstanceMethods)
>       end
>     end
>   end
>
>   module InstanceMethods
>     private
>     def prepare_user
>       session[:user] ||= Member.find_by_id(2) # When there's no user_id
> in the session, then use #2 for Guest
>     ...
>   end
>
> Because I extracted this functionality from an application, in
> prepare_user() there's still a hardwired "Member" model used.
> But in another application I need this to be a "User" model, so
> I'd like to be able to specify the model to use in the options
> hash of the performs_authorization() method. So how can I
> achieve this? Do I have to use define_method() in the context of
> performs_authorization? This would work, I guess, but I don't like
> it very much... Isn't there another way?

A simple way consists in storing the options hash as a class
variable, you can then create instance and class method
to get the class from the options hash :

def performs_authorization(options = {})
   before_filter :prepare_user

   cattr_accessor :options
   self.options = options

   include(InstanceMethods)
end

# give the name you want
def user_model
   options[:user_model]
end

module InstanceMethods
  private
  def user_model
     self.class.user_model
  end

  def prepare_user
    session[:user] ||= user_model.find_by_id(2)
     ...
  end
end

HTH,

   -- Jean-François.