CODEWITHSUNDEEP
rubymodule
bkahler
bkahler

Reputation: 365

Ruby Invoking Module Method On Extend

Given a basic ruby class and module, is there a way to call a method from the module as soon as an instance of the class is extended ?

class Dog 
  def initialize(name)
    @name = name 
  end 
end

module Speech
  def say_name
    puts @name
  end
  # call to method in module ?
  say_name
end

fido = Dog.new('fido')
fido.extend Speech    => *'fido'*

I am aware of the 'included' method that acts sort of like a callback when a module is included, but I was hoping for something similar for extend.

Upvotes: 4

Views: 458

Answers (1)

Arup Rakshit
Arup Rakshit

Reputation: 118261

Here is one trick using the method extend_object.

Extends the specified object by adding this module’s constants and methods (which are added as singleton methods). This is the callback method used by Object#extend.

class Dog 
  def initialize(name)
    @name = name 
  end 
end

module Speech
  def Speech.extend_object(o)
    super
    puts o.say_name
  end

  def say_name
    @name
  end
end

fido = Dog.new('fido')
fido.extend Speech # 'fido'

Upvotes: 3

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