All we have ever worked with an application with legacy code. Refactoring is a technique that allows us to restructure and redesign our application code without changing its behavior so that it is more readable and easier to maintain. This presentation discusses the advantages and disadvantages of refactoring as well as some of the main techniques that apply during a refactoring.

1. Making tastier code through
Refactoring

2. Person.new(
name: 'Gabriel Ortuño',
job: 'ASPgems',
web: 'arctarus.com',
pet_project: 'rezets.com',
github: 'arctarus',
twitter: 'arctarus'
)

3. 1. Introduction
2. Sample
3. Conclusions

4. Refactoring?

5. "Refactoring is the process of changing a
software system in such a way that it
does not alter the external behavior of
the code yet improves its internal
structure"
Martin Fowler

7. Code Smells

8. Refactoring Toolbox

9. Why?

10. Green Field

11. Legacy Code

12. When?

14. 1. Introduction
2. Sample
3. Conclusions

15. New Task
Print nutritional report in HTML

16. Recipe
Ingredient
name 1:N
ingredients amount
food
nutritional_report
1:1
Food
HIGH
LOW
REGULAR
name
nutritional_code

18. class Recipe
...
def nutritional_report
total_calories, nutritional_points = 0, 0
result = "Nutritional Report for #{name}n"
self.ingredients.each do |ingredient|
this_calories = 0
# add calories by ingredient
case ingredient.food.nutritional_code
when Food::HIGH
this_calories += 5
this_calories += (ingredient.amount - 2) * 1.5 if ingredient.amount > 2
when Food::LOW
this_calories += ingredient.amount * 3
when Food::REGULAR
this_calories += 1.5
this_calories += (ingredient.amount - 3) * 1.5 if ingredient.amount > 3
end
# add nutritional points
nutritional_points += 1
# add extra nutritional points for high food
if ingredient.food.nutritional_code == Food::HIGH && ingredient.amount > 1
nutritional_points += 1
end
# show figures for this rental
result += "t" + ingredient.food.name + "t" + this_calories.to_s + "n"
total_calories += this_calories
end
# add footer lines
result += "Total calories are #{total_calories}n"
result += "You earned #{nutritional_points} nutritional points"
result
end
end

19. Whyyyy?

20. 1º Build a solid set of tests

21. describe Recipe do
let(:recipe) { Recipe.new("Lentils with chorizo") }
let(:chorizo) { Food.new('chorizo', Food::HIGH) }
let(:lentil) { Food.new('lentil', Food::LOW) }
let(:potatoe) { Food.new('potatoe', Food::REGULAR) }
it "has a name" do
recipe.name.should == "Lentils with chorizo"
end
describe "calories" do
it "without ingredients are 0"
it "with one regular ingredient are 1.5"
it "with one regular ingredient and amount > 3 are 3"
it "with one high ingredient are 5"
end
...
end

22. $ rspec spec
..............
Finished in 0.00742 seconds
14 examples, 0 failures

23. class Recipe
...
def nutritional_report
total_calories, nutritional_points = 0, 0
result = "Nutritional Report for #{name}n"
self.ingredients.each do |ingredient|
this_calories = 0
# add calories by ingredient
case ingredient.food.nutritional_code
when Food::HIGH
this_calories += 5
this_calories += (ingredient.amount - 2) * 1.5 if ingredient.amount > 2
when Food::LOW
this_calories += ingredient.amount * 3
when Food::REGULAR
this_calories += 1.5
this_calories += (ingredient.amount - 3) * 1.5 if ingredient.amount > 3
end
# add nutritional points
nutritional_points += 1
# add extra nutritional points for high food
if ingredient.food.nutritional_code == Food::HIGH && ingredient.amount > 1
nutritional_points += 1
end
# show figures for this rental
result += "t" + ingredient.food.name + "t" + this_calories.to_s + "n"
total_calories += this_calories
end
# add footer lines
result += "Total calories are #{total_calories}n"
result += "You earned #{nutritional_points} nutritional points"
result
end
end

24. Long Method

25. Comments

26. class Recipe
...
def nutritional_report
total_calories, nutritional_points = 0, 0
result = "Nutritional Report for #{name}n"
self.ingredients.each do |ingredient|
this_calories = 0
# add calories by ingredient
case ingredient.food.nutritional_code
when Food::HIGH
this_calories += 5
this_calories += (ingredient.amount - 2) * 1.5 if ingredient.amount > 2
when Food::LOW
this_calories += ingredient.amount * 3
when Food::REGULAR
this_calories += 1.5
this_calories += (ingredient.amount - 3) * 1.5 if ingredient.amount > 3
end
# add nutritional points
nutritional_points += 1
# add extra nutritional points for high food
if ingredient.food.nutritional_code == Food::HIGH && ingredient.amount > 1
nutritional_points += 1
end
# show figures for this rental
result += "t" + ingredient.food.name + "t" + this_calories.to_s + "n"
total_calories += this_calories
end
# add footer lines
result += "Total calories are #{total_calories}n"
result += "You earned #{nutritional_points} nutritional points"
result
end
end

27. ...
# add calories by ingredient
case ingredient.food.nutritional_code
when Food::HIGH
this_calories += 5
this_calories += (ingredient.amount - 2) * 1.5 if ...
when Food::LOW
this_calories += ingredient.amount * 3
when Food::REGULAR
this_calories += 1.5
this_calories += (ingredient.amount - 3) * 1.5 if ...
end
...

28. Extract Method

29. class Recipe
...
def calories_for(ingredient)
case ingredient.food.nutritional_code
when Food::HIGH
this_calories += (ingredient.amount - 2) * 1.5 if ...
this_calories += 5
when Food::LOW
this_calories += ingredient.amount * 3
when Food::REGULAR
this_calories += (ingredient.amount - 3) * 1.5 if ...
this_calories += 1.5
end
end
end

30. def nutritional_report
total_calories, nutritional_points = 0, 0
result = "Nutritional Report for #{name}n"
self.ingredients.each do |ingredient|
this_calories = calories_for(ingredient)
# add nutritional points
nutritional_points += 1
# add extra nutritional points for high food
if ingredient.food.nutritional_code == Food::HIGH && ingredient.
amount > 1
nutritional_points += 1
end
# show figures for this rental
result += "t" + ingredient.food.name + "t" + this_calories.to_s +
"n"
total_calories += this_calories
end
# add footer lines
result += "Total calories are #{total_calories}n"
result += "You earned #{nutritional_points} nutritional points"
result
end

31. $ rspec spec
.FFFFFFFFFFFFF
Finished in 0.00742 seconds
14 examples, 13 failures

33. class Recipe
...
def calories_for(ingredient)
case ingredient.food.nutritional_code
when Food::HIGH
this_calories += (ingredient.amount - 2) * 1.5 if ...
this_calories += 5
when Food::LOW
this_calories += ingredient.amount * 3
when Food::REGULAR
this_calories += (ingredient.amount - 3) * 1.5 if ...
this_calories += 1.5
end
end
end

34. class Recipe
...
def calories_for(ingredient)
this_calories = 0
case ingredient.food.nutritional_code
when Food::HIGH
this_calories += (ingredient.amount - 2) * 1.5 if ...
this_calories += 5
when Food::LOW
this_calories += ingredient.amount * 3
when Food::REGULAR
this_calories += (ingredient.amount - 3) * 1.5 if ...
this_calories += 1.5
end
end
end

35. $ rspec spec
..............
Finished in 0.00742 seconds
14 examples, 0 failures

36. class Recipe
...
def calories_for(ingredient)
this_calories = 0
case ingredient.food.nutritional_code
when Food::HIGH
this_calories += (ingredient.amount - 2) * 1.5 if ...
this_calories += 5
when Food::LOW
this_calories += ingredient.amount * 3
when Food::REGULAR
this_calories += (ingredient.amount - 3) * 1.5 if ...
this_calories += 1.5
end
end
end

37. class Recipe
...
def calories_for(ingredient)
this_calories = 0
case ingredient.food.nutritional_code
when Food::HIGH
this_calories += (ingredient.amount - 2) * 1.5 if ...
this_calories += 5
when Food::LOW
this_calories += ingredient.amount * 3
when Food::REGULAR
this_calories += (ingredient.amount - 3) * 1.5 if ...
this_calories += 1.5
end
end
end

38. Feature Envy

39. Move Method

40. class Ingredient
...
def calories
this_calories = 0
case food.nutritional_code
when Food::HIGH
this_calories += 5
this_calories += (amount - 2) * 1.5 if amount > 2
when Food::LOW
this_calories += amount * 3
when Food::REGULAR
this_calories += 1.5
this_calories += (amount - 3) * 1.5 if amount > 3
end
end
end

41. class Recipe
def nutritional_report
total_calories, nutritional_points = 0, 0
result = "Nutritional Report for #{name}n"
self.ingredients.each do |ingredient|
# add nutritional points
nutritional_points += 1
# add extra nutritional points for high food
if ingredient.food.nutritional_code == Food::HIGH && ingredient.
amount > 1
nutritional_points += 1
end
# show figures for this rental
result += "t" + ingredient.food.name + "t"
result += ingredient.calories.to_s + "n"
total_calories += ingredient.calories
end
# add footer lines
result += "Total calories are #{total_calories}n"
result += "You earned #{nutritional_points} nutritional points"
result
end
end

42. describe Ingredient do
let(:chorizo) { Food.new('chorizo',Food::HIGH) }
let(:lentil) { Food.new('lentil', Food::LOW) }
let(:potatoe) { Food.new('potatoe', Food::REGULAR) }
describe 'calories' do
it "with one regular food are 1.5"
it "with one regular food and amount > 3 are 3"
it "with one high food are 5"
it "with one high food and amount > 2 are 6.5"
it "with one low food are 3"
end
end

43. $ rspec spec
...................
Finished in 0.00588 seconds
19 examples, 0 failures

44. class Recipe
def nutritional_report
total_calories, nutritional_points = 0, 0
result = "Nutritional Report for #{name}n"
self.ingredients.each do |ingredient|
# add nutritional points
nutritional_points += 1
# add extra nutritional points for high food
if ingredient.food.nutritional_code == Food::HIGH &&
ingredient.amount > 1
nutritional_points += 1
end
# show figures for this rental
result += "t" + ingredient.food.name + "t"
result += ingredient.calories.to_s + "n"
total_calories += ingredient.calories
end
# add footer lines
result += "Total calories are #{total_calories}n"
result += "You earned #{nutritional_points} nutritional points"
result
end
end

45. Remove
Feature Envy
with
Extract Method

46. class Ingredient
...
def nutritional_points
if food.nutritional_code == Food::HIGH && amount > 1
2
else
1
end
end
end

47. class Recipe
...
def nutritional_report
total_calories, nutritional_points = 0, 0
result = "Nutritional Report for #{name}n"
self.ingredients.each do |ingredient|
nutritional_points += ingredient.nutritional_points
# show figures for this rental
result += "t" + ingredient.food.name + "t"
result += ingredient.calories.to_s + "n"
total_calories += ingredient.calories
end
# add footer lines
result += "Total calories are #{total_calories}n"
result += "You earned #{nutritional_points} nutritional point
result
end
end

48. describe Ingredient do
describe "nutritional points" do
it "is 2 if food is high and amount > 1"
it "is 1 if food is high and amount = 1"
it "is 1 if food is not high and amount = 1"
it "is 1 if food is not high and amount > 1"
end
end

49. $ rspec spec
.......................
Finished in 0.00588 seconds
23 examples, 0 failures

50. class Recipe
def nutritional_report
total_calories, nutritional_points = 0, 0
result = "Nutritional Report for #{name}n"
self.ingredients.each do |ingredient|
nutritional_points += ingredient.nutritional_points
# show figures for this rental
result += "t" + ingredient.food.name + "t"
result += ingredient.calories.to_s + "n"
total_calories += ingredient.calories
end
# add footer lines
result += "Total calories are #{total_calories}n"
result += "You earned #{nutritional_points} nutritional point
result
end
end

51. Replace Temp with Query

52. class Recipe
...
def total_calories
ingredients.sum(:calories)
end
def total_nutritional_points
ingredients.sum(:nutritional_points)
end
end

53. class Recipe
def nutritional_report
result = "Nutritional Report for #{name}n"
ingredients.each do |ingredient|
# show figures for this rental
result += "t" + ingredient.food.name + "t"
result += ingredient.calories.to_s + "n"
end
# add footer lines
result += "Total calories are #{total_calories}n"
result += "You earned #{total_nutritional_points} nutritional
result
end
...
end

54. $ rspec spec
.......................
Finished in 0.00621 seconds
23 examples, 0 failures

55. class Recipe
def nutritional_report
result = "Nutritional Report for #{name}n"
ingredients.each do |ingredient|
# show figures for this rental
result += "t" + ingredient.food.name + "t"
result += ingredient.calories.to_s + "n"
end
# add footer lines
result += "Total calories are #{total_calories}n"
result += "You earned #{total_nutritional_points} nutritional
result
end
...
end

56. HTML Report
class Recipe
def html_nutritional_report
result = "<h1>Nutritional Report for #{name}</h1>"
ingredients.each do |ingredient|
# show figures for this rental
result += "<p>#{ingredient.food.name} "
result += "{ingredient.calories}</p>"
end
# add footer lines
result += "<p>Total calories are #{total_calories}</p>"
result += "<p>You earned #{total_nutritional_points} "
result += "nutritional points</p>"
result
end
...
end

57. More Refactoring?
Replace Method
with Method Objet
Template Method Pattern

58. class NutritionalReport
def initialize(recipe)
@recipe = recipe
end
def output
head
body
foot
end
def head
...
def body
...
def line(ingredient)
...
def foot
...
end

59. class HTMLNutritionalReport < NutritionalReport
def head
"<h1>Nutritional Report for #{name}</h1>"
end
def line(ingredient)
"<p>#{ingredient.food.name} #{ingredient.calories}</p>"
end
def foot
result = "<p>Total calories are #{@recipe.total_calories}</p
result += "<p>You earned #{@recipe.total_nutritional_points}
nutritional points</p>"
result
end
end

60. WIN!

61. class Ingredient
...
def calories
this_calories = 0
case food.nutritional_code
when Food::HIGH
this_calories += (amount - 2) * 1.5 if amount > 2
this_calories += 5
when Food::LOW
this_calories += amount * 3
when Food::REGULAR
this_calories += (amount - 3) * 1.5 if amount > 3
this_calories += 1.5
end
end
def nutritional_points
(food.nutritional_code == Food::HIGH && amount > 1) ? 2 : 1
end
...
end

62. I notice a weird smell...
Could it be envy?

63. Get rid of
Feature Envy
with
Move Method

64. class Food
def calories(amount)
this_calories = 0
case nutritional_code
when HIGH
this_calories += (amount - 2) * 1.5 if amount > 2
this_calories += 5
when LOW
this_calories += amount * 3
when REGULAR
this_calories += (amount - 3) * 1.5 if amount > 3
this_calories += 1.5
end
end
def nutritional_points(amount)
(nutritional_code == HIGH && amount > 1) ? 2 : 1
end
end

65. class Ingredient
def calories
food.calories(amount)
end
def nutritional_points
food.nutritional_points(amount)
end
end

66. describe Ingredient do
let(:chorizo) { Food.new('chorizo', Food::HIGH) }
let(:lentil) { Food.new('lentil', Food::LOW) }
let(:potatoe) { Food.new('potatoe', Food::REGULAR) }
describe 'calories' do
it "with one regular food are 1.5"
it "with one regular food and amount > 3 are 3"
it "with one high food are 5"
it "with one high food and amount > 2 are 6.5"
it "with one low food are 3"
end
describe "nutritional points" do
it "is 2 if food is high and amount > 1"
it "is 1 if food is high and amount = 1"
it "is 1 if food is not high and amount = 1"
it "is 1 if food is not high and amount > 1"
end
end

67. $ rspec spec/
................................
Finished in 0.00865 seconds
32 examples, 0 failures

68. class Food
def calories(amount)
this_calories = 0
case nutritional_code
when HIGH
this_calories += (amount - 2) * 1.5 if amount > 2
this_calories += 5
when LOW
this_calories += amount * 3
when REGULAR
this_calories += (amount - 3) * 1.5 if amount > 3
this_calories += 1.5
end
end
def nutritional_points(amount)
(nutritional_code == HIGH && amount > 1) ? 2 : 1
end
end

69. Fix
Switch Statements
Replace Type Code with
State/Strategy

70. class Food
...
def nutritional_code=(value)
@nutritional_code = value
@nutritional_type = case @nutritional_code
when HIGH then HighNutritional.new
when LOW then LowNutritional.new
when REGULAR then RegularNutritional.new
end
end
def calories(amount)
@nutritional_type.calories(amount)
end
def nutritional_points(amount)
@nutritional_type.points(amount)
end
end

71. module DefaultNutritionalPoints
def points(amount)
1
end
end
class RegularNutritional
include DefaultNutritionalPoints
def calories(amount)
acum = 1.5
acum += (amount - 3) * 1.5 if amount > 3
acum
end
end

72. class LowNutritional
include DefaultNutritionalPoints
def calories(amount)
amount * 3
end
end
class HighNutritional
def calories(amount)
acum = 5
acum += (amount - 2) * 1.5 if amount > 2
acum
end
def points(amount)
amount > 1 ? 2 : 1
end
end

73. EPIC
WIN!

74. 1. Introduction
2. Sample
3. Conclusions

75. No Silver Bullet

76. Improve Design

77. Helps find bugs

78. Program faster

79. Good programmers write
code that humans can
understand

80. Refactor
to Win

81. ¡Thanks!

82. Questions?

83. References
● Refactoring: Improving design of existing
code - Martin Fowler
● Refactoring to Patterns - Joshua Kerievsky
● Clean Code - Robert C. Martin
● Design Patterns in Ruby - Russ Olsen
● Source Making
http://sourcemaking.com/refactoring

84. Tools
● Reek - Code Smell Detector for ruby
https://github.com/troessner/reek
● Rails Best Practices
http://rails-bestpractices.com
● Code Climate
http://codeclimate.com
● Ruby Refactoring Tool for Vim
https://github.com/ecomba/vim-ruby-refactoring

85. Thanks!