How to wrap an array in Ruby

wrap_array.rb

require "forwardable"

# How to wrap an array

class Foo

  extend Forwardable

  def_delegator :@a, :each
  include Enumerable

  def initialize
    @a = []
  end

  def grow
    @a << 0
  end

  def has_two?
    @a.size == 2
  end
   
end

foo = Foo.new
foo.grow
p foo.has_two?    # => false
foo.grow
p foo.has_two?    # => true