Active support concern handling

activesupportconcern.rb

# Test1
module M
  def foo
    puts "M"
  end  
end

module N
 include M 
 def foo
  puts "N"
  super 
 end 
end
include N
Object
=> Object
>> foo
N
M
module A
  module Concern
    def self.extended(base)
      puts "inside extended #{base}"
      base.instance_variable_set("@_dependencies", [])
    end

    def append_features(base)
          puts "inside append #{base}"
      if base.instance_variable_defined?("@_dependencies")
        base.instance_variable_get("@_dependencies") << self
        return false
      else
        return false if base < self
        @_dependencies.each { |dep| base.send(:include, dep) }
        super
        base.extend const_get("ClassMethods") if const_defined?("ClassMethods")
        base.send :include, const_get("InstanceMethods") if const_defined?("InstanceMethods")
        base.class_eval(&@_included_block) if instance_variable_defined?("@_included_block")
      end
    end

    def included(base = nil, &block)
       puts "inside included #{base}"
      if base.nil?
        @_included_block = block
      else
        super
      end
    end
  end
end  


module Foo
     extend A::Concern
     puts "Begin Foo"
     included do
       class_eval do
         def self.method_injected_by_foo
           puts "Injected Method"
         end
       end
     end
   end

   module Bar
     extend A::Concern
     include Foo
     puts "Begin BAr"
     included do
       puts "Calleing Injected Method frombar"
       self.method_injected_by_foo
     end
   end

   class Host
     include Bar # works, Bar takes care now of its dependencies
   end