From: Edoardo Rossi <edd.rossi@...>
Date: 2013-05-06T16:48:48+09:00
Subject: Re: Hash return is not correct

On Mon, May 6, 2013 at 9:19 AM, Peter Hickman
<peterhickman386@googlemail.com> wrote:
> No the output is correct. Your mistake is assuming that Router.new will
> return the same object for the same input parameters. For example:
>
> frequency = Hash.new(0)
> models = %w(2000 3000 2000 3200)
> models.each{|m| frequency[Router.new('Linksys',m)] += 1}
>
>
> p frequency => {
>
> #<Router:0x10f80ae70 @model="3000", @make="Linksys">=>1,
>
> #<Router:0x10f80ae20 @model="2000", @make="Linksys">=>1,
>
> #<Router:0x10f80aec0 @model="2000", @make="Linksys">=>1,
>
> #<Router:0x10f80add0 @model="3200", @make="Linksys">=>1
>
> }
>
>
> Note each entry is a different object. This is the normal and correct
> behaviour. When you do:
>
> puts frequency[Router.new('Linksys','2000')]
>
> I assume you meant this and not Car.new it creates yet another object which
> of course is not in the hash and so returns 0.
>
>

Maybe the example in the Hash docs could be useful to the OP:

http://ruby-doc.org/core-2.0/Hash.html
Quoting:
"
Hash Keys
Two objects refer to the same hash key when their hash value is
identical and the two objects are eql? to each other.
A user-defined class may be used as a hash key if the hash and eql?
methods are overridden to provide meaningful behavior. By default,
separate instances refer to separate hash keys.
A typical implementation of hash is based on the object’s data while
eql? is usually aliased to the overridden == method:
(...)
"

I hope this helps.

e.