#Create a namespace for your modules and classes
module ActsAsMonkey


  #Create a module for extensions to AR. I know all this seperating
  #methods into ClassMethods, SingletonMethods and InstanceMethods and
  #using all this Ruby magic to actually include them can seem overly
  #complicated, but there are a few advantages to this approach. It all
  #depends on what you're doing, but for an acts_as-style plugin you only
  #want to include SingletonMethods and InstanceMethods when the acts_as
  #method is run. It also makes it easier to document them.
  module ActiveRecordExtensions
  
    #Gets run when this module is included into another module or class.
    #This way you can just include ActiveRecordExtensions in AR::B, and
    #it'll take care of the rest itself.
    def self.included(base)
      #base == ActiveRecord::Base, usually
      base.send(:extend, ClassMethods)
    end
  
    
    #Class methods will be available to all classes that inherit AR::B
    module ClassMethods
    
      #This method extends the class in which it's run
      def acts_as_monkey
        extend SingletonMethods
        include InstanceMethods
        
        #As this is a class method, you have access to all the other
        #class methods in AR::B too, such as validations
        validates_presence_of :name
        
        #And callbacks
        before_validation :check_color
        before_save :upcase_name
      end
    
    end
    
    
    #Singleton methods are added to a single class. I.e. they're
    #class methods, but only for the classes that have "acts_as_monkey"
    #in them.
    module SingletonMethods
    
      def default_color
        'brown'
      end
    
    end
    
    
    #Each instance of a class that acts_as_monkey will have these methods.
    module InstanceMethods
    
      def smile
        'Monkey smile :-]'
      end
      
      
      private
      
        def upcase_name
          self.name.upcase!
        end
        
        
        def check_color
          if respond_to?('color=')
            self.color ||= self.class.default_color
          end
        end
    
    end
  
  
  end
  
  
  #Will be available in all controllers
  module ActionControllerExtensions
  
    #before_filter has to be run _after_ this module
    #has been included into AC::B, because it's not going
    #to be available until then.
    def self.included(base)
      #and it doesn't hurt to check then either
      base.send(:before_filter, :foo) if respond_to?(:before_filter)
    end
  
    #Was this page requested by a monkey?
    def monkey_request?
      request.env['User-Agent'] =~ /monkey/
    end
    
    private
      def foo
        #..
      end
  
  end
  
  
  #Will be available in views. "Helper methods"
  module ActionViewExtensions
  
    def whatever(monkey)
      "I'm the whatever monkey, my name is #{monkey.name} and my fur is #{monkey.color}"
    end
  
  end


end