From: "David A. Black" <dblack@...>
Date: 2008-10-03T03:17:30+09:00
Subject: Re: Problem extending (adding methods) to class

Hi --

On Fri, 3 Oct 2008, Nit Khair wrote:

> I am trying to extend a class developed by someone else (its from the
> ncurses-ruby lib). I need to add some fields and methods to it.
>
> 1. I tried directly extending it the usual way.
>    class MyForm < FORM
>
>  However, all attempts to access my methods would give a NoMethodError
> on the base class Ncurses::FORM.

Methods you add to a subclass are not visible to instances of the
original class.

> 2. I then looked up the source and copied the following *on top* of my
> class MyForm.
>
>  module Form
>    class FORM
>      attr_reader :user_object
>
>      def user_object=(obj)
>        @user_object = obj
>      end
>    end
> end
>
> I changed user_object to "my_fields". This approach works, but means i
> cannot actually extend the class. I need a heirarchy below this each
> adding its methods and data.
>
> Now I am wondering whether my approach is wrong. Is the class
> locked/final in some way?

No. If you want to add methods to it, you can just open it up and add
them:

   require 'rubygems'
   require 'ncurses'

   class Ncurses::Form::FORM
     def my_method
       puts "Hello"
     end
   end

   n = Ncurses::Form::FORM.new
   n.my_method                    # Hello


David

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