From: cremes.devlist@...
Date: 2006-03-03T10:30:53+09:00
Subject: Nuby - why does my #inspect misbehave?

I'm working through a few exercises to teach myself Ruby. One of them  
is the creation of a deck of cards along with all the usual  
operations one performs upon them.

I override the Object#inspect method to pretty-print my card values,  
but it doesn't always get called. Whether or not it gets called  
depends on the **absence** of a line in #print_playing_deck. Here is  
my code stripped down to the basics.

class Card < Object
   attr_reader :suit, :value

   protected
   attr_writer :suit, :value

   public
   def initialize(suit = "Joker", value = 15)
     @suit = suit
     @value = value
   end

   def inspect
       puts "#{self.value} of #{self.suit}s"
   end
end

class CardDeck < Card
   attr_reader :size

   SUITSIZE = 13

   def initialize(size = 52)
     @size = size

     @playing_deck = Array.new(@size) do |index|
       case index
       when *(0..12)
         Card.new("Heart", index + 1)
       end
     end
     @number_remaining = @playing_deck.length
   end

   def print_playing_deck
     @playing_deck.each do |card|
       puts card
     end
     # WEIRD!! If I have any code after this loop, my Card#inspect is  
not called.
     # In this case I have a "puts" but it could even be arithmetic  
expressions preventing
     # the #inspect from working
     #puts "#{@playing_deck.length} cards in deck"
   end

end


And here is the output:


irb(main):001:0> load 'ex.rb'
=> true
irb(main):002:0> d=CardDeck.new(5)
of s
=>
irb(main):003:0> d.print_playing_deck
#<Card:0x65b4>
#<Card:0x63e8>
#<Card:0x62a8>
#<Card:0x61cc>
#<Card:0x6168>
5 cards in deck
=> nil
######## comment out the "puts" in #print_playing_deck and reload
irb(main):004:0> load 'ex.rb'
./ex.rb:22: warning: already initialized constant SUITSIZE
=> true
irb(main):005:0> d.print_playing_deck
#<Card:0x65b4>
#<Card:0x63e8>
#<Card:0x62a8>
#<Card:0x61cc>
#<Card:0x6168>
1 of Hearts
2 of Hearts
3 of Hearts
4 of Hearts
5 of Hearts
=> [, , , , ]

I don't understand why my Card#inspect method doesn't print anything  
to stdout when there is code after the loop. Is this just a weird  
artifact of irb?

BTW, running on OSX with darwinports Ruby 1.8.4.