Module Tidbits

I always forget what including versus extending a Module, so here's a little reminder for myself. 
module UsefulMethods
  def some_cool_thing
    1 + 1 == 0
  end
end

class IncludeUsefulInstanceMethods
  include UsefulMethods
end

class IncludeUsefullClassMethods
  extend UsefulMethods
end

puts IncludeUsefulInstanceMethods.new.some_cool_thing # => false
puts IncludeUsefullClassMethods.some_cool_thing # => false
So, including a module basically shoves the module's methods into the class as instance methods, while extending a module puts them in as class methods. That's it. By the way, this was inspired by Dave Thomas' metaprogramming talk at the Rails Edge Studio in Denver.

Posted by Lee Marlow Thu, 16 Nov 2006 11:35:06 GMT

Read full article no comments