Martin-Nyaga

class TicketFactory
  def self.ticket_for opts
    class_for(opts[:vehicle_type]).new(opts)
  end

  # Method to auto generate class from a vehicle_type
  # e.g "Private car" => PrivateCarParkingTicket
  #     "Matatu" => MatatuParkingTicket
  def self.class_for vehicle_type
    prefix = vehicle_type.underscore.parameterize("_").camelize

Martin-Nyaga

class TicketFactory
  TICKET_CLASSES = {
    'Truck' => TruckParkingTicket,
    'Matatu' => MatatuParkingTicket,
    'Public Bus' => PublicBusParkingTicket
  }

  def self.ticket_for opts
    # .fetch takes a second argument as a default if the 
    # key is not found

Martin-Nyaga

parking_ticket = TicketFactory.ticket_for(opts)
# where opts is the hash for options

Martin-Nyaga

class TicketFactory
  def self.ticket_for opts
    class_for(opts[:vehicle_type]).new(opts)
  end

  def self.class_for vehicle_type
    case vehicle_type
    when 'Truck'
      TruckParkingTicket
    when 'Matatu'

Martin-Nyaga

class PublicBusParkingTicket < ParkingTicket
  def total_cost
    @eet_passed == true ? surcharge : super
  end
end

Martin-Nyaga

class MatatuParkingTicket < ParkingTicket
  def base_fee
    1100
  end

  def surcharge
    weekdays.inlcude?(@day) ? super * 1.5  : super
  end

  private

Martin-Nyaga

class TruckParkingTicket < ParkingTicket
  def base_fee
    1200
  end

  def surcharge
    super * 1.5
  end
end

Martin-Nyaga

class ParkingTicket
  def initialize(opts)
    @day = opts[:day] || raise(":day is required")
    @vehicle_type = opts[:vehicle_type] || raise(":vehicle_type is required")
    @eet_passed = opts[:eet_passed] || raise(":eet_passed is required")
    ... 
  end

  def base_fee
    1000

Martin-Nyaga

def beat_up thing
  ...
  thing.make_sound
  ...
end
# thing can be an Animal, or a Dog, and this code will work.

Martin-Nyaga

class Animal
  def initialize(name)
    @name = name
  end

  def make_sound
    puts "No sound"
  end
end