This page contains automated test results for code from O'Reilly's Ruby Cookbook. If this code looks interesting or useful, you might want to buy the whole book.

Sorting an Array by an Attribute of its Objects
CodeExpectedActual
[5.01, -5, 0, 5].sort
 [-5, 0, 5, 5.01] [-5, 0, 5, 5.01] 
["Utahraptor", "Ankylosaur", "Maiasaur"].sort
["Ankylosaur", "Maiasaur", "Utahraptor"] ["Ankylosaur", "Maiasaur", "Utahraptor"] 
arrays = [[1,2,3], [100], [10,20]]
arrays.sort_by { |x| x.size }
 [[100], [10, 20], [1, 2, 3]] [[100], [10, 20], [1, 2, 3]] 
[1, 100, 42, 23, 26, 10000].sort do |x, y| 
  x == 42 ? 1 :  x <=> y
end
 [1, 23, 26, 100, 10000, 42] [1, 23, 26, 100, 10000, 42] 
class Animal
 attr_reader :name, :eyes, :appendages
 def initialize(name, eyes, appendages)
  @name, @eyes, @appendages = name, eyes, appendages
 end
 def inspect
  @name
 end
end
animals = [Animal.new("octopus", 2, 8), 
           Animal.new("spider", 6, 8),
           Animal.new("bee", 5, 6),
           Animal.new("elephant", 2, 4),
           Animal.new("crab", 2, 10)]
animals.sort_by { |x| x.eyes }
 [octopus, elephant, crab, bee, spider] [octopus, elephant, crab, bee, spider] 
animals.sort_by { |x| x.appendages  }
 [elephant, bee, octopus, spider, crab] [elephant, bee, octopus, spider, crab]