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@alvinncx
Last active October 10, 2020 08:10
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Refactoring exercise #1
class Price
def price_code; end
def charge; end
def frequent_renter_points
1
end
class Childrens
def price_code; Movie::CHILDRENS; end
def charge(days_rented)
result = 1.5;
if days_rented > 3
result = result + (days_rented - 3) * 1.5
end
return result
end
end
class NewRelease
def price_code; Movie::NEW_RELEASE; end
def charge(days_rented)
result = days_rented * 3
end
def frequent_renter_points
days_rented > 1 ? 2 : 1
end
end
class RegularPrice
def price_code; Movie::REGULAR; end
def charge(days_rented)
result = 2;
if days_rented > 2
result = result + (days_rented - 2) * 1.5
end
return result
end
end
end
class Movie < ActiveRecord::Base
has_many :rentals
CHILDRENS = 2
REGULAR = 0
NEW_RELEASE = 1
attribute :title, :string
attribute :price_code, :int
attr_accessor :price
def initialize
case price_code
when REGULAR
@price = Price::Regular.new
when CHILDRENS
@price = Price::Childrens.new
when NEW_RELEASE
@price = Price::NewRelease.new
end
end
def price_code
@price.price_code
end
def frequent_renter_points(days_rented)
@price.frequent_renter_points(days_rented)
end
def charge(days_rented)
@price.charge(days_rented)
end
end
class Rental < ActiveRecord::Base
belongs_to :movie
belongs_to :customer
attribute :days_rented, :int
def frequent_renter_points
movie.frequent_rental_points(days_rented)
end
def charge
movie.charge(days_rented)
end
end
class Customer < ActiveRecord::Base
has_many :rentals
attribute :name, :string
def total_charge
rentals.map(&:charge).sum
end
def total_frequent_renter_points
rentals.map(&:frequent_renter_points).sum
end
def statement
result = "Rental Record for #{name} \n"
rentals.for_each { |rental|
result << "\t#{rental.movie.title}\t#{rental.charge}\n"
}
result << "Amount owed is #{total_charge}\n"
result << "You earned #{total_frequent_renter_points} frequent renter points"
return total_amount
end
end
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alvinncx commented Oct 10, 2020

Play though the Gist Revisions to see each refactoring step

Tried to refactor the piece of code introduced in the opening chaper of Refactoring: Improving the Design of Existing Code by Martin Folwer. It was originally in Java, I've tried to follow the exercise in Ruby.

Techniques used here

  • Extract Method
  • Move Method
  • Replace Conditional with Polymorphism
  • Replace Type Code with State
  • Delegation

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