From: Rob Boellaard <rboell@...>
Date: 2008-06-15T04:56:23+09:00
Subject: Re: Knowing which subclass called a superclass class method

Hi David,

  This time I really made the class ;-)


class S

attr_accessor :my_ivar

    def self.inherited(c)
         c.class_eval {
           @my_ivar = self.name
         }

    end

  def initialize
    puts "In S initialize, my_ivar = #{@my_ivar}"
    super
  end


  def self.do_something
    puts "In S class-method do_something, my_ivar = #{@my_ivar}"
  end

end


 and,

require "s"


class B < S


  def initialize
    super
  end

  def show_my_ivar

    puts "In show_my_ivar " + @my_ivar
  end

end


when I do B.do_something, @my_ivar is "B" as it should
but if I do B.new, my_ivar is nil

  To solve it I can modify initialize like:

  def initialize
      @my_ivar = self.class.to_s
    puts "In S initialize, my_ivar = #{@my_ivar}"
    super
  end

and
b = B.new
puts b.show_my_ivar

works properly.

 But as this is a simplification, in my real app I need a few lines of 
code to set @my_ivar, and I 'd rather not have too much duplicate code.

  I guess what I am trying for is to configure a variable, using the 
name of the subclass, that is readily available to both class methods 
and instance methods.


  thanks a lot,

  Rob




-- 
Posted via http://www.ruby-forum.com/.