How to add methods to existing classes

Say I have a horse racing ruby application that allow people to know information about every competing horses. I have an input box that people can use to enter the name of a horse. Once they click OK, information about the specified horse is displayed to the user.

Instead of going the traditonal route, how about adding a “horse” method to the String class? It could not be easier :

HORSES = [
  {
    :name => "Jolly Jumper", 
    :also_known_as => ["Smart Arse","Lucky Luke friend"], 
    :speed => 3, :intelligence => 30, 
    :favorite_quote => "I am a horse, I don’t have quotes"
  },
  
  {
    :name => "Incredibly Bad", 
    :also_known_as => ["Shame","The Pathetic"], 
    :speed => 2, :intelligence => 4, 
    :favorite_quote => "If you still put your money on me, you only have yourself to blame"
  },
 
  {
    :name => "Fast And Furious", 
    :also_known_as => ["The Strong Rebel","The Furious One"], 
    :speed => 50, :intelligence => 15, 
    :favorite_quote => "I am fast"
  },
  
 {
    :name => "Slow and Jerky", 
    :also_known_as => ["Tender","Terrible Choice"], 
    :speed => 1, :intelligence => 10, 
    :favorite_quote => "Pick me once, regret it for a lifetime."
  }
]
 
class String
  def horse
    res = HORSES.select { |h| h[:name] == self || h[:also_known_as].include?(self)}
    res.first if res.length>0
  end
end
 
#Then you can do stuff like this :
horse = "Tender".horse
if horse
        puts "#{horse[:name]}, also known as #{horse[:also_known_as].join(", ")}, has a speed of #{horse[:speed]} and an intelligence of #{horse[:intelligence]}. In its free time, this horse like to become all philosophic, look at the sky and say : ‘#{horse[:favorite_quote]}’"
else
        puts "This horse doesn’t exists in our records"
end

Talk about some great syntactic ruby sugar!

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Posted under : short & sweet

2 Comments

Remember people to be nice in your comments. I have no problem if you formulate a constructive remark but offensive comments will be removed as soon as they get here. You stay polite or you go elsewhere, it’s that simple. Now I will put an emoticon to convince you all that I am not angry: :)

Comment by : Frank

— June 29, 2010 @ 4:30 pm

class String
def horse
HORSES.detect { |h| h[:name] == self || h[:also_known_as].include?(self) }
end
end

Comment by : Justin

— July 1, 2010 @ 1:19 pm

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