Making tastier code through Refactoring

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.

Transcript

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 name ingredients nutritional_report Ingredient amount food Food name nutritional_code HIGH LOW REGULAR 1:N 1:1
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. 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 HTML Report
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. Feature Envy Move Method Get rid of with
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. Replace Type Code with State/Strategy Switch Statements Fix
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!