Comments on: Comparing custom objects in Ruby using uniq.

By: Jeremy

Jeremy — Wed, 16 Dec 2009 21:48:02 +0000

DUDE! Nice. This clears up some stuff too.

By: Tim Matheson

Tim Matheson — Sun, 08 Feb 2009 18:21:37 +0000

Very entertaining.

By: Rabbit

Rabbit — Fri, 25 Jan 2008 23:25:27 +0000

Interesting information on the #hash method. However, we’re both right and both wrong. I should know better than to type code directly into WordPress… (My example code differs from the code I was using in console.)

The example code as I have it works if all you define is eql?. However, if you find existing clients, each with a unique ID, it doesn’t.

It works with new objects because nil.hash is the same as nil.hash.

It doesn’t work with found objects because 1.hash is not 2.hash.

We override the name attribute of Client because “Rabbit”.hash is the same as “Rabbit”.hash.

Thanks for pointing that out. =)

I’ll edit the post to reflect the new information.

By: Russ Smith

Russ Smith — Thu, 24 Jan 2008 23:38:59 +0000

You only have to override the eql? method. :D

The hash method is part of ActiveRecord and is defined as:

def hash
id.hash
end

The hash method that is part of all objects creates a sort of checksum of the value passed.