Sorting an array of objects in Ruby by object attribute?

Question

I have an array of objects in Ruby on Rails. I want to sort the array by an attribute of the object. Is it possible?

Answer 1

You can make any class sortable by overriding the <=> method:

class Person

  attr_accessor :first_name, :last_name

  def initialize(first_name, last_name)
    @first_name = first_name
    @last_name = last_name
  end

  def <=>(other)
    @last_name + @first_name <=> other.last_name + other.first_name
  end

end

Now an array of Person objects will be sortable on last_name.

ar = [Person.new("Eric", "Cunningham"), Person.new("Homer", "Allen")]

puts ar  # => [ "Eric Cunningham", "Homer Allen"]  (Person objects!)

ar.sort!

puts ar  # => [ "Homer Allen", "Eric Cunningham" ]