From: Robert Klemme <shortcutter@...>
Date: 2006-09-25T05:20:14+09:00
Subject: Re: Adding a new method to a class

Mickael Faivre-Macon wrote:
> Hi,
> 
> What is called the process of adding a new method of an already defined 
> class ?
> 
> For example:
> 
> class A
>   def a
>   end
> end
> 
> And in another file:
> 
> class A
>   def b
>   end
> end
> 
> And now my real question:
> 
> What if I want to declare a new class variable in the initialize method ?
> If it's a derived class I can call super:
> def initialize
>   super
>   @my_var = ""
> end
> 
> but if it not derived ?
> How can I do this ?

You can alias the old initialize method and replace it with another one:

irb(main):014:0> class A
irb(main):015:1>   def initialize(x)
irb(main):016:2>     @foo = x
irb(main):017:2>   end
irb(main):018:1> end
=> nil
irb(main):019:0> a = A.new 10
=> #<A:0x38e4d0 @foo=10>
irb(main):020:0> class A
irb(main):021:1>   alias initialize_old initialize
irb(main):022:1>   def initialize(x)
irb(main):023:2>     initialize_old x
irb(main):024:2>     @bar = "foo"
irb(main):025:2>   end
irb(main):026:1> end
=> nil
irb(main):027:0> b = A.new 20
=> #<A:0x374610 @bar="foo", @foo=20>

Kind regards

	robert