enum.rb

enum.rb

# >> color = Enum.new("red", "green", "blue")
# >> color.values
# => ["red", "green", "blue"]
# >> color["red"]
# => "red"
# >> color["yellow"]
# ArgumentError: Invalid value: "yellow". Allowed: "red", "green", "blue".
class Enum
  def initialize(*values)
    @values = values
  end

  attr_reader :values

  def [](value)
    unless values.include?(value)
      raise ArgumentError, "Invalid value: #{value.inspect}. Allowed: #{values.map(&:inspect).join(", ")}."
    end

    value
  end
end

if __FILE__ == $0
  require 'minitest/autorun'

  begin
    require 'minitest/doctest'
  rescue LoadError
    puts "minitest-doctest not found. Follow these steps until there's a gem release:"
    puts "  git clone [email protected]:lauri/minitest-doctest.git"
    puts "  cd minitest-doctest"
    puts "  rake install"
  end

  Minitest::Doctest.run(__FILE__)
end