Defines a bunch of helper methods for polymorphic associations.

polymorphic_entity.rb

module PolymorphicEntity
  
  module ActiveRecordExtension
    
    # Defines a bunch of helper methods for polymorphic associations.
    def has_polymorphic_entity(*associations)
      
      associations.each do |assoc|
      
        # def sender_entity
        #   self.sender_id ? "#{self.sender_type}##{self.sender_id}" : nil
        # end      
        define_method("#{assoc}_entity") do
          self.send("#{assoc}_id") ? "#{self.send("#{assoc}_type")}##{self.send("#{assoc}_id")}" : nil
        end
        
        # def sender_entity=(polymorphic_id)
        #   type, id = polymorphic_id.to_s.split("#")
        #   self.sender_type = type
        #   self.sender_id   = id  
        # end
        define_method("#{assoc}_entity=") do |polymorphic_id|
          if polymorphic_id.present?
            type, id = polymorphic_id.to_s.split("#")
            self.send("#{assoc}_type=", type)
            self.send("#{assoc}_id=", id)        
            self.send("#{assoc}").reload  
          else
            self.send("#{assoc}=", nil)
          end
        end
        
        # def sender_changed?
        #   sender_id_changed? || sender_type_changed?
        # end
        define_method("#{assoc}_changed?") do
          send("#{assoc}_id_changed?") || send("#{assoc}_type_changed?")
        end
        
        # def sender_was
        #   (self.sender_type_was || self.sender_type).constantize.find(self.sender_id_was || self.sender_id) 
        # end
        define_method("#{assoc}_was") do
          type = send("#{assoc}_type_was") || send("#{assoc}_type")
          id   = send("#{assoc}_id_was") || send("#{assoc}_id")
          type && id ? type.constantize.find_by_id(id) : nil
        end
        
        # Define some class helpers...
        self.class.instance_eval do
          # def where_sender_is(sender)
          #   where("#{table_name}.sender_id = ? and #{table_name}.sender_type = ?", sender.id, sender.class.base_class.name)
          # end
          define_method("where_#{assoc}_is") do |entity|
            where("#{table_name}.#{assoc}_id = ? and #{table_name}.#{assoc}_type = ?", entity.id, entity.class.base_class.name)
          end
          
          # def where_sender_is_not(sender)
          #   where("#{table_name}.sender_id <> ? OR #{table_name}.sender_type <> ?", sender.id, sender.class.base_class.name)
          # end
          define_method("where_#{assoc}_is_not") do |entity|
            where("#{table_name}.#{assoc}_id <> ? OR #{table_name}.#{assoc}_type <> ?", entity.id, entity.class.base_class.name)
          end
        end
        
        
      end
      
    end
    
  end
  
  ActiveRecord::Base.send(:extend, PolymorphicEntity::ActiveRecordExtension)  
end