From: gruby@... (John)
Date: 2003-09-10T06:26:44+09:00
Subject: Eval

I am trying to create a class with attributes that are values
retrieved from a database. E.g.

class Item
  attr_accessor :color
  def initialize(color)
    @color = color
  end
end

z = Item.new("yellow")

resultset = {"fruit" => "banana"}

I'd like to now set an accessor for z.fruit and set the value to
banana.

Is there a define_attribute method like there's a define_method
method?

To put it succinctly, how can I create instance attributes after the
instance has already been created? Here's my greenhorn attempt, but I
wonder if I'm hurting performance by invoking eval or if there's a
more accepted way to do it:

  def add_attribute(name, val)
    instance_eval <<-EOD
      def #{name}= (val)
        @#{name} = val
      end
      def #{name}
        @#{name}
      end
      @#{name} = "#{val}"
    EOD
  end

z.add_attribute( resultset[0], resultset[1] )
puts z.fruit  #banana