CODEWITHSUNDEEP
rubymoduleclass-method
markzzz
markzzz

Reputation: 48045

Why am I not able to call a parent-class method from module?

This is my code:

module RubyEditExtComponent
    def eventExt
        watchExt "banana"
    end
end

class RubyEditExt
    def self.watchExt(value)
        puts value
    end

    include RubyEditExtComponent
end

RubyEditExt.new.eventExt

I want to call a specific (parent) class method that will output the value I'll pass to it. But it says undefined method watchExt.

Where am I wrong?

Upvotes: 0

Views: 79

Answers (2)

guitarman
guitarman

Reputation: 3320

May be, what you are trying to do is to extend your class RubyEditExt with functionality from the module RubyEditExtComponent. This has nothing to do with inheritance (ChildClass < ParentClass). Usually you will do this to modularize functionality, which keeps your classes clean and the modules are reusable. Such modules are called mixins.

See the example below. This way you can extend your class with instance methods which you can call for every object of your class or you define class methods for the class which will include the module. 

module RubyEditExtComponent
  def self.included(klass)
    klass.instance_eval do
      include InstanceMethods
      extend ClassMethods
    end
  end

  module InstanceMethods
    def eventExt
      watchExt "banana"
    end
  end

  module ClassMethods
    def eventExt2
      self.new.watchExt "banana"
    end
  end
end

class RubyEditExt
  include RubyEditExtComponent

  def watchExt(value)
    puts value
  end
end

The method self.included is called at the inclusion of the module (include RubyEditExtComponent) and it receives the class which includes it. Now you can call the instance method for an object of your class:

RubyEditExt.new.eventExt
banana
 => nil

Or you call the class method. In this method I create an instance (self.new) of the class which includes the module (self == RubyEditExt) and then I call the instance method watchExt for it.

RubyEditExt.eventExt2
banana
=> nil

Upvotes: 1

Aleksei Matiushkin
Aleksei Matiushkin

Reputation: 121010

watchExt is called from the instance method, so it either should be an instance method itself:

class RubyEditExt
  def watchExt(value) # NO self
    puts value
  end
  ...
end

or it should be called as class method:

module RubyEditExtComponent
  def eventExt
    self.class.watchExt "banana"
  end
end

Upvotes: 1

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