How do I add 'each' method to Ruby object (or should I extend Array)?

Question

I have an object Results that contains an array of result objects along with some cached statistics about the objects in the array. I\'d like the Results object to

Answer 1

Your << method is perfectly fine and very Ruby like.

To make a class act like an array, without actually inheriting directly from Array, you can mix-in the Enumerable module and add a few methods.

Here's an example (including Chuck's excellent suggestion to use Forwardable):

# You have to require forwardable to use it
require "forwardable"

class MyArray
  include Enumerable
  extend Forwardable

  def initialize
    @values = []
  end

  # Map some of the common array methods to our internal array
  def_delegators :@values, :<<, :[], :[]=, :last

  # I want a custom method "add" available for adding values to our internal array
  def_delegator :@values, :<<, :add

  # You don't need to specify the block variable, yield knows to use a block if passed one
  def each
    # "each" is the base method called by all the iterators so you only have to define it
    @values.each  do |value| 
      # change or manipulate the values in your value array inside this block
      yield value
    end
  end

end

m = MyArray.new

m << "fudge"
m << "icecream"
m.add("cake")

# Notice I didn't create an each_with_index method but since 
# I included Enumerable it knows how and uses the proper data.
m.each_with_index{|value, index| puts "m[#{index}] = #{value}"}

puts "What about some nice cabbage?"
m[0] = "cabbage"
puts "m[0] = #{m[0]}"

puts "No! I meant in addition to fudge"
m[0] = "fudge"
m << "cabbage"
puts "m.first = #{m.first}"
puts "m.last = #{m.last}"

Which outputs:

m[0] = fudge
m[1] = icecream
m[2] = cake
What about some nice cabbage?
m[0] = cabbage
No! I meant in addition to fudge
m.first = fudge
m.last = cabbage