Developing Rails plugin: need some metaprog. help

Ruby
1

Hi all

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?

Thanks
Josh

2

Maybe I can pass arguments to include() somehow?

include(InstanceMethods, model_to_use)

?

3

Maybe I can pass arguments to include() somehow?

include(InstanceMethods, model_to_use)

That should be fine. Until you try to access it, it’s just a variable.
You can have

variable.do_something()

and then later assign different objects to that variable. e.g.:

def sound(beast)
beast.make_noise
end

and then

sound(Cow) # => “moo”
sound(Dog) # => “woof”
sound(Rabbit) # => “squee”

–
Giles B.

Podcast: http://hollywoodgrit.blogspot.com
Blog: http://gilesbowkett.blogspot.com
Portfolio: http://www.gilesgoatboy.org
Tumblelog: http://giles.tumblr.com

4

Hi Joshua,

  def performs_authorization(options = {})
  session[:user] ||= Member.find_by_id(2) # When there's no user_id

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.

5

Thank you, Jean-François! But is this good style? I’m always looking for
well written patterns, and maybe I should dig deeper into Rails for
having a better overwiew about how they do things. :slight_smile: