From: Phrogz <phrogz@...>
Date: 2007-11-15T12:45:00+09:00
Subject: Re: adding an attribute to an object

On Nov 14, 7:10 pm, Mark Volkmann <r.mark.volkm...@mac.com> wrote:
> I know how to add new methods to an existing object, but is there a way to add an attribute?
> I know I can do it if the object was created with ObjectStruct, but what if it is a "normal" Ruby object?

As Pat pointed out, there are no 'attributes' in Ruby, just methods.
(Those methods may or may not have a 1-to-1 correspondence to instance
variables; that's all the convenience methods like attr_accessor do,
is set up a simple method.)

irb(main):001:0> o = Object.new
=> #<Object:0x1dbbf4>
irb(main):002:0> def o.duration=( seconds )
irb(main):003:1>   @length = seconds
irb(main):004:1> end
=> nil
irb(main):005:0> def o.duration; @length; end
=> nil
irb(main):006:0> o.duration = 120
=> 120
irb(main):007:0> puts o.duration
120
=> nil
irb(main):008:0> def o.duration_in_minutes; @length / 60; end
=> nil
irb(main):009:0> puts o.duration_in_minutes
2
=> nil