refactoring_example.rb

class Price
  attr_reader :price_code
  
  def get_price_code
    @price_code
  end
  
  def get_charge(days_rented)
    # To implement in the subclass
    raise NotImplemeted
  end
  
  def get_frequent_renter_points(days_rented)
    1
  end
end

class RegularPrice < Price  
  def initialize
    @price_code = 0
  end

  def get_charge(days_rented)
    result = 2
    result += (days_rented - 2) * 1.5 if days_rented > 2
    result
  end
end

class NewReleasePrice < Price
  def initialize
    @price_code = 1
  end

  def get_charge(days_rented)
    days_rented * 3
  end
  
  def get_frequent_renter_points(days_rented)
    # add bonus for a two day new release rental
    days_rented > 1 ? 2 : 1
  end
end

class ChildrenPrice < Price
  def initialize
    @price_code = 2
  end

  def get_charge(days_rented)
    result = 1.5
    result += (days_rented - 3) * 1.5 if days_rented > 3
    result
  end
end

class Movie
  REGULAR = 0
  NEW_RELEASE = 1
  CHILDREN = 2

  attr_reader :title
  attr_reader :price_code

  def initialize(title, price_code)
    @title = title
    @price_code = case price_code
                  when NEW_RELEASE
                    NewReleasePrice.new
                  when CHILDREN
                    ChildrenPrice.new
                  else
                    RegularPrice.new
                  end
  end
  
  def get_charge(days_rented)
    @price_code.get_charge days_rented
  end

  def get_price_code
    @price_code.get_price_code
  end
  
  def get_frequent_renter_points(days_rented)
    @price_code.get_frequent_renter_points days_rented
  end
end

class Rental
  attr_reader :movie, :days_rented

  def initialize(movie, days_rented)
    @movie, @days_rented = movie, days_rented
  end

  def get_charge
    @movie.get_charge @days_rented
  end
  
  def get_frequent_renter_points
    @movie.get_frequent_renter_points @days_rented
  end
end

class Customer
  attr_reader :name

  def initialize(name)
    @name = name
    @rentals = []
  end

  def add_rental(arg)
    @rentals << arg
  end
  
  def get_total_charge
    total = 0
    @rentals.each { |rental| total += rental.get_charge }
    total
  end
  
  def get_total_frequent_renter_points
    total = 0
    @rentals.each { |rental| total += rental.get_frequent_renter_points }
    total
  end

  def statement
    result = "Rental Record for #{@name}\n"

    @rentals.each do |rental|
      # show figures for this rental
      result += "\t" + rental.movie.title + "\t" + rental.get_charge.to_s + "\n"
    end

    #add footer lines
    result += "Amount owed is #{get_total_charge}\n"
    result += "You earned #{get_total_frequent_renter_points} frequent renter points"
    result
  end
end