LEVEL 5: MODULES

gistfile1.rb

Image.ancestors        # [Image, ImageUtils, Object, Kernel, BasicObject]
Image.included_modules # [ImageUtils, Kernel]

class Image
  image = Image.new
  image.extend(ImageUtils)
  image.preview # an object is extending the module
end

# the module will not be available in other objects
image = Image.new
image.preview  # NoMethodError: undefined method `preview' for #<Image:0x10b448a98>



module ImageUtils
  def self.included(base)
    base.extend(ClassMethods)
    base.clean_up
  end

  module ClassMethods
    def fetch_from_twitter(user)
    end

    def clean_up
    end
  end
end

require 'active_support/concern'
module ImageUtils
  extend ActiveSupport::Concern
  
  included do
    clean_up
  end

  module ClassMethods
    def fetch_from_twitter(user)
    end

    def clean_up
    end
  end
end