From: N Okia <wrecklass1@...>
Date: 2006-08-01T12:20:03+09:00
Subject: Re: check if 2 objects are equal

If you want to define equivalence for your classes, you really need to
do so yourself.

The easiest way is to make the class Comparable, and define your own
<=> operator. You can be as simple or as complex as you like:

class MyClass
  include Comparable

  attr_accessor :my_age, :my_first_name, :my_last_name

  def initialize(age,first_name,last_name)
    @my_age = age.to_i
    @my_first_name = first_name
    @my_last_name = last_name
  end

  def <=>(other)
    # if the other class being compared is nil, we aren't equivalent
    return nil if other.nil?

    # Simple case, if both objects have same objectid, they are the same
    return 0 if object_id == other.object_id

    # Define a heirarchy of tests for this class
    if (@my_age == other.my_age)
      if (@my_first_name <=> other.my_first_name) == 0
        return @my_last_name <=> other.my_last_name
      else
        return @my_first_name <=> other.my_first_name
      end
    else
      return @my_age <=> other.my_age
    end
  end

end