Rails acts_as_* plugins, with parameters

11155 · February 25, 2010, 12:32pm

Hi all, I'm trying to write a plugin which will allow me to specify: acts_as_item :option=>:value

i need to be able to access the :options=>:value hash from instances of the model also. I've tried with class_eval in the plugin, but can't get it working. I'm calling acts_as_item(options), and that method can see the options passed from a model. Then inside the class_eval, I'm adding a method (def self.configuration) which returns the options hash. I thought from an instance, I'd be able to do instance.class.configuration which would then return said options hash.

Any ideas? thanks for reading.

module Item #called by active record for us def self.included(base) base.extend ClassMethods end

module ClassMethods def acts_as_item(options = {}) configuration = {:option=>:value} class_eval { include InstanceMethods

def self.configuration puts "in def acts_as_item (#{configuration})\n\n" end } end end

module InstanceMethods def item_name puts self.class.configuration end end end

Frederick_Cheung · February 25, 2010, 1:07pm

I'd probably add accessor methods for a class variable (or something like class_inheriting_accessor) and then call that accessor method from your acts_as_item method

Fred

Rick_DeNatale · February 25, 2010, 1:08pm

I think you want this to be def configuration

Since this is in a module extended by the class.

11155 · February 25, 2010, 2:24pm

Hi Rick, Fred, I got the behavior i was looking for by using class variables in the class_eval block: class_eval { include InstanceMethods @@config = options def conf @@config end }

instances can then do instance.conf and returns the options hash. I tried using class methods, and used def configuration, rather than def self., but I still couldnt' get that working. I'm still going to try and get it working that way as well, as I'd like to understand it a bit more.

I've looked at the code for the acts_as_tree module, and they're achieving this

github.com

rails/acts_as_tree/blob/master/lib/active_record/acts/tree.rb

module ActiveRecord
  module Acts
    module Tree
      def self.included(base)
        base.extend(ClassMethods)
      end

      # Specify this +acts_as+ extension if you want to model a tree structure by providing a parent association and a children
      # association. This requires that you have a foreign key column, which by default is called +parent_id+.
      #
      #   class Category < ActiveRecord::Base
      #     acts_as_tree :order => "name"
      #   end
      #
      #   Example:
      #   root
      #    \_ child1
      #         \_ subchild1
      #         \_ subchild2
      #

This file has been truncated. show original

from line 42. the configuration hash is available from within the class methods (self.roots and self.root), and on line 91 there's "self.class.roots" - which is what I was trying to do initially.

hrmmmm

Frederick Cheung wrote:

Hi all, I'm trying to write a plugin which will allow me to specify: acts_as_item :option=>:value

i need to be able to access the :options=>:value hash from instances of the model also. I've tried with class_eval in the plugin, but can't get it working.

I'd probably add accessor methods for a class variable (or something like class_inheriting_accessor) and then call that accessor method from your acts_as_item method

Fred

Rick Denatale wrote: