From: Dave Thomas <Dave@...>
Date: 2002-07-23T13:28:12+09:00
Subject: Re: attr_reader for great number of instance vars

michael libby <x@ichimunki.com> writes:

> The attr_reader line looks clumsy to me. Is there a way to get the class to 
> automatically allow for any instance variable to be given the attr_reader 
> characteristic?

THe class doesn't know it's instance variables: they only appear in
the actually instances when first used (that is, each instance could
potentially have a different set of instance variables). The code
below is kind of dangerous, but dynamically defines reader methods for
any otherwise unknown method call:

   class Dave

      def method_missing(name, *args)
        fail "No one expects the extra args" unless args.empty?
        type.class_eval "attr_reader :#{name}"
        send name
      end

      def initialize
        @a = 1
        @b = "cat"
        @c = /abc/
      end
   end

   d = Dave.new

   p d.a
   p d.b
   p d.c


If there was some point at which you knew all your instance variables
were set, you could always use the Object#instance_variables method to
iterate over them and create accessors.


Cheers


Dave