From: dblack@...
Date: 2003-01-26T14:46:43+09:00
Subject: Re: Reflection for instance variables?

Hi --

On Sun, 26 Jan 2003, Patrick Narkinsky wrote:

> Hi.  I'm brand new to Ruby, so please pardon if this question is naive,

Welcome to Ruby!

> but I have not been able to figure it out. I would like to come up with
> a way to define a method in a superclass that would give me a list of
> variables in a subclass.  So:
>
> class Father
>    @h_test = "1234"
>    @h_test2 = "12345"
>
>    def Father.vars
>      return self.instance_vars # This does not work.

I think you mean "instance_variables".

>    end
> end
>
> class Son < Father
>    @h_test3 = "123456"
> end
>
> print Son::vars
>
> ## end listing
>
> Would give me ['h_test', 'h_test2', 'h_test3'].  It seems to me that
> the key would be to get a reference to the Class object for the
> subclass, but can't seem to figure out how to do that. Suggestions?

I'm not 100% sure what you mean, but let me try something which
probably isn't what you mean, and maybe you can bridge the gap or
bounce it back:

  class Father
    def self.report_ivs
      ancestors.map {|a| a.instance_variables}.flatten.compact
    end
    @x = 1
    @y = 2
  end

  class Son < Father
    @z = 3
  end

  p Father.report_ivs     # ["@y", "@x"]
  p Son.report_ivs        # ["@z", "@y", "@x"]


David

-- 
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav