From: daz <dooby@...10.karoo.co.uk>
Date: 2004-03-03T15:44:45+09:00
Subject: Re: why are Hashes so unsorted? what's your solution?


"Ruby Baby" wrote:
> I try to avoid questions like "Why doesn't Ruby do what ___ does?"

Go on, force yourself ;)

>
> SELECT sku, artistname, albumtitle, sold FROM albums
> ORDER BY sold DESC LIMIT 20;
>
> When I get the hash of results from the database, I'm used to making
> the "sku" the hash key since it's the only unique identifier.
> A perfect hash key.  Used everywhere by my iteration methods.
>
> In PHP, this is no problem.  I get the hash, and I can do the
> "each" iteration on it, and get my top-selling albums in order.
>

Sounds to me that you get an ordered hash - a special form of hash.

> In Ruby, it's an unordered jumble.

That's a hash;  across the universe.

> Why is that?

The answer to that would probably irritate you more than is necessary;
but, in short, because it's a Hash.

>
> And what do you think is the Ruby way solution for what I need to do?
>
>
> (The simple query I gave above was much simpler, but I have lots and
> lots of MySQL queries where I want the results to come back in the
> order that MySQL gave them, but with full access to the hash results.)
>

You've ruled out one option; of omitting the ORDER BY clause then
using Enumerable#sort_by on the hash before iterating -- so I won't
bring that up.

> Thanks!

I'm not done, yet.

Or you could use a container which maintains its order - the Array
which, in your case, might be an array of hashes.

[{:sku => 10, :artist=>'Global Communication', :albumtitle => 'Pentamerous Metamorphosis'},
 {:sku => 54, :artist=>'Eat Static',           :albumtitle => 'Abduction'},
 {...}
]


There'll be other ways, I'm sure ;)


daz