Sample of ruby yield methods, modules and includes...

ruby_oop_sample

class Array
  def each_valid
    self.each do |val|
      valid = yield val
      puts val if valid
    end
  end

  def map
    internal_array = []
    self.each do |val|
      internal_array << yield(val) if block_given?
    end
    internal_array
  end

  def map_tuple
    internal_array = []
    prev = nil
    self.each do |val|
      internal_array << yield(prev, val) if block_given?
      prev = val
    end
    internal_array
  end
end

module IterateHelpers
  def each_valid
    self.each do |val|
      valid = yield val
      puts val if valid
    end
  end
end

class Stand
  include Enumerable
  include IterateHelpers

  attr_accessor :cars

  def initialize(cars)
    @cars = cars
  end

  def cars
    @cars
  end

  def each
    cars.each do |car|
      yield car
    end
  end

  def cars=(cars)
    self.cars = cars
  end
end

class Car
  include Enumerable

  def <=>(other)
    return 1 if car.horse_power > other.horse_power
    return -1 if car.horse_power < other.horse_power
    0
  end
end