From: Tim Hunter <sastph@...>
Date: 2006-08-01T21:30:10+09:00
Subject: Re: check if 2 objects are equal

N Okia wrote:
> 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
> 

The simplest way to do this is:

def <=>(other)
	return [@my_age, @my_first_name, @my_last_name] <=> [other.age, 
other.my_first_name, other.my_last_name]
end