ruby: can module execute initialization code automatically?

Question

I've put some functionality in a module, to be extended by an object. I'd like the functionality to be executed automatically when the module is extended. However, it has to be executed in the context of the instance, not Module.

module X
   extend self

   @array = [1,2,3]

end
obj.extend(X)

Currently, @array does not get created in the instance. I don't wish to force the developer to call some initialization method, since then for each Module he needs to know the name of a unique method to call. Is this possible ?

Victor Deryagin · Accepted Answer · 2011-12-28 07:29:43Z

11

You can use Module#extended hook for execution code on extension and BasicObject#instance_exec (or BasicObject#instance_eval) for executing arbitrary code in context of extended object:

module X
  def self.extended(obj)
    obj.instance_exec { @array = [1,2,3] }
  end
end

class O
  attr_reader :array
end

obj = O.new

obj.array                                 # => nil

obj.extend(X)

obj.array                                 # => [1, 2, 3]

edited Dec 28, 2011 at 7:29

answered Dec 28, 2011 at 7:22

Victor Deryagin

12.3k1 gold badge32 silver badges38 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

rahul Over a year ago

Thanks to both Victor and avy.

avy · Accepted Answer · 2011-12-28 07:16:57Z

4

Show this article

module Math
  def self.extended(base)
    # Initialize module.
  end
end

answered Dec 28, 2011 at 7:16

avy

5723 silver badges10 bronze badges

Collectives™ on Stack Overflow

ruby: can module execute initialization code automatically?

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related