From: Brian Mattern <brian.mattern@...>
Date: 2006-03-09T00:25:26+09:00
Subject: Re: Newbie: sorting an array of custom objects

On Wednesday 08 March 2006 08:48, Einar H淡st wrote:

>
> That solution requires some_field to be 'naturally' ordered, though,
> doesn't it? (I'm very new to Ruby...) What if some_field contains a
> string, and I want 'Oranges' to be sorted before 'Apples'? Actually, I'm
> writing a card game, so I want 'Spades' < 'Hearts' < 'Clubs' < 'Diamonds'.
>
> - Einar

Ideally you would have a Card class that has value and suit fields. Then you 
could implement <=> and just use Array#sort.

Alternatively, if you want to sort a specific way just the one time, you can 
pass a block to sort which takes two parameters |a,b| and returns -1 if a < 
b, 0 if a == b and 1 if a >b.

So, you could do something like:

#an array of suit strings
SUITS = %w{Spades Hearts Clubs Diamonds}

# use a simple array for each card for this example
cards = [[3, 'Clubs'], [2, 'Spades'], [10, 'Diamonds'], [5, 'Clubs'], [7, 
'Hearts']]

sorted = cards.sort { |a, b| 
  ord = SUITS.index(a.last) <=> SUITS.index(b.last) #sort by suit
  ord = a.first <=> b.first if ord = 0 #suit matched, so sort value
  ord
}
 
#print out the cards in sorted order
puts sorted.map{ |card| "#{card.first} of #{card.last}" }.join(', ')

--
Brian Mattern