car.rb

RPM_TO_SPEED_MULTIPLIER = 10

class Tire
  def initialize(producer:, diameter:)
    @producer = producer
    @diameter = diameter
    @dirty = [true, false].sample
  end

  def dirty
    @dirty
  end
end

class Engine
  def initialize(capacity:, horses:)
    @capacity = capacity
    @horses = horses
    @rpm = 0
    @dirty = [true, false].sample
    @is_electric = true
  end

  def accelerate(kilometers)
    # Lets say that our speed increase linearly with rotations per second.
    @rpm += kilometers * RPM_TO_SPEED_MULTIPLIER
  end

  def rpm
    @rpm
  end

  def is_electric?
    @is_electric
  end

  def dirty
    @dirty
  end
end

class Car
  include Enumerable
  
  def initialize(name:, engine:, tires:)
    @name = name
    @engine = engine
    @tires_pack = tires
  end

  my_delegate :rpm, :accelerate, :horses, :is_electric?, to: :@engine

  my_delegate :each, to: :details

  my_delegate :capitalize, to: :@name

  def speed
    rpm * RPM_TO_SPEED_MULTIPLIER
  end

  def details # => Array
    @tires_pack + [@engine]
  end
end

def test_1
  engine = Engine.new(capacity: 0, horses: 200)
  tire1 = Tire.new(producer: :michelin, diameter: 17)
  tire2 = Tire.new(producer: :michelin, diameter: 17)

  tire3 = Tire.new(producer: :good_year, diameter: 18)
  tire4 = Tire.new(producer: :good_year, diameter: 18)

  c = Car.new(name: 'Nissan', engine: engine, tires: [tire1, tire2, tire3,tire4])
  
  assert_equal c.horses, 200
  assert_equal c.capitalize, 'Nissan'.capitalize
end

engine = Engine.new(capacity: 0, horses: 200)
tire1 = Tire.new(producer: :michelin, diameter: 17)
tire2 = Tire.new(producer: :michelin, diameter: 17)

tire3 = Tire.new(producer: :good_year, diameter: 18)
tire4 = Tire.new(producer: :good_year, diameter: 18)

c = Car.new(name: 'Nissan', engine: engine, tires: [tire1, tire2, tire3,tire4])

pp "INITIAL: speed: #{c.speed}"
c.accelerate(10)
pp "ACCELERATE 1: speed #{c.speed}, rpm: #{c.rpm}"
c.accelerate(20)
pp "ACCELERATE 2: speed #{c.speed}, rpm: #{c.rpm}"

pp c.each { |detail| pp detail.to_s }

pp "Finding engine details:"
pp c.find { |detail| detail.is_a?(Engine) }

pp "Finding dirty details:"
pp c.find_all {|detail| detail.dirty }