Clean Code

A fuller version of my previous clean code presentation

Transcript

1. clean code from theory to practice by Luís Zamith
2. Clean Code TAKING YOUR PROGRAMS TO THE LAUNDRY
4. 1. Looks like you cared
5. 1. Looks like you cared 2. Pretty much what you expected
6. 1. Looks like you cared 2. Pretty much what you expected 3. Language looks as perfect fit for problem
7. 1. Looks like you cared 2. Pretty much what you expected 3. Language looks as perfect fit for problem My definition
8. circular friction reduction device with central axis
9. circular friction reduction device with central axis =
10. Design Patterns circular friction reduction device with central axis =
11. class Report def initialize @title = 'Monthly Report' @text = [ 'Things are going', 'really, really well.' ] end ! def output_report ...HTML specific stuff... end end template method: reports
12. bad code class Report def initialize @title = 'Monthly Report' @text = [ 'Things are going', 'really, really well.' ] end ! def output_report ...HTML specific stuff... end end template method: reports
13. template method: reports class Report def initialize @title = 'Monthly Report' @text = ['Things are going', 'really, really well.'] end ! def output_report output_start output_head @text.each do |line| output_line(line) end output_end end ! def output_start; end ! def output_head output_line(@title) end ! def output_line(line) raise 'Called abstract method: output_line' end ! def output_end; end end
14. template method: reports better code class Report def initialize @title = 'Monthly Report' @text = ['Things are going', 'really, really well.'] end ! def output_report output_start output_head @text.each do |line| output_line(line) end output_end end ! def output_start; end ! def output_head output_line(@title) end ! def output_line(line) raise 'Called abstract method: output_line' end ! def output_end; end end
15. Design Principles THE THEORY BEHIND THE THEORY
16. Optimize for Readability and Maintainability
17. S
    O
    L
    I
    D Uncle Bob Martin
18. S
    O
    L
    I
    D ingle responsibility Uncle Bob Martin
19. class Invitation < ActiveRecord::Base! EMAIL_REGEX = /\A([^@\s]+)@((:?[a-z0-9]+\.)+[a-z]{2,})\z/i! STATUSES = %w(pending accepted)! ! belongs_to :sender, class_name: 'User'! belongs_to :survey! ! before_create :set_token! ! validates :recipient_email, presence: true, format: EMAIL_REGEX! validates :status, inclusion: { in: STATUSES }! ! def to_param! token! end! ! def deliver! Mailer.invitation_notification(self).deliver! end! ! private! ! def set_token! self.token = SecureRandom.urlsafe_base64! end! end
20. class Invitation < ActiveRecord::Base! EMAIL_REGEX = /\A([^@\s]+)@((:?[a-z0-9]+\.)+[a-z]{2,})\z/i! STATUSES = %w(pending accepted)! ! belongs_to :sender, class_name: 'User'! belongs_to :survey! ! before_create :set_token! ! validates :recipient_email, presence: true, format: EMAIL_REGEX! validates :status, inclusion: { in: STATUSES }! ! def to_param! token! end! ! def deliver! Mailer.invitation_notification(self).deliver! end! ! private! ! def set_token! self.token = SecureRandom.urlsafe_base64! end! end
21. class TokenizedModel < SimpleDelegator! def save! __getobj__.token ||= SecureRandom.urlsafe_base64! __getobj__.save! end! ! def to_param! __getobj__.token! end! end TokenizedModel.new(invitation) Decorator Pattern
22. class Invitation < ActiveRecord::Base! EMAIL_REGEX = /\A([^@\s]+)@((:?[a-z0-9]+\.)+[a-z]{2,})\z/i! STATUSES = %w(pending accepted)! ! belongs_to :sender, class_name: 'User'! belongs_to :survey! ! validates :recipient_email, presence: true, format: EMAIL_REGEX! validates :status, inclusion: { in: STATUSES }! ! def deliver! Mailer.invitation_notification(self).deliver! end! end
23. Responsibility = Reason to Change
24. class Invitation < ActiveRecord::Base! EMAIL_REGEX = /\A([^@\s]+)@((:?[a-z0-9]+\.)+[a-z]{2,})\z/i! STATUSES = %w(pending accepted)! ! belongs_to :sender, class_name: 'User'! belongs_to :survey! ! before_create :set_token! ! validates :recipient_email, presence: true, format: EMAIL_REGEX! validates :status, inclusion: { in: STATUSES }! ! def to_param! token! end! ! def deliver! Mailer.invitation_notification(self).deliver! end! ! private! ! def set_token! self.token = SecureRandom.urlsafe_base64! end! end
25. class Invitation < ActiveRecord::Base! EMAIL_REGEX = /\A([^@\s]+)@((:?[a-z0-9]+\.)+[a-z]{2,})\z/i! STATUSES = %w(pending accepted)! ! belongs_to :sender, class_name: 'User'! belongs_to :survey! ! before_create :set_token! ! validates :recipient_email, presence: true, format: EMAIL_REGEX! validates :status, inclusion: { in: STATUSES }! ! def to_param! token! end! ! def deliver! Mailer.invitation_notification(self).deliver! end! ! private! ! def set_token! self.token = SecureRandom.urlsafe_base64! end! end
26. class Invitation < ActiveRecord::Base! EMAIL_REGEX = /\A([^@\s]+)@((:?[a-z0-9]+\.)+[a-z]{2,})\z/i! STATUSES = %w(pending accepted)! ! belongs_to :sender, class_name: 'User'! belongs_to :survey! ! before_create :set_token! ! validates :recipient_email, presence: true, format: EMAIL_REGEX! validates :status, inclusion: { in: STATUSES }! ! def to_param! token! end! ! def deliver! Mailer.invitation_notification(self).deliver! end! ! private! ! def set_token! self.token = SecureRandom.urlsafe_base64! end! end
27. class Invitation < ActiveRecord::Base! EMAIL_REGEX = /\A([^@\s]+)@((:?[a-z0-9]+\.)+[a-z]{2,})\z/i! STATUSES = %w(pending accepted)! ! belongs_to :sender, class_name: 'User'! belongs_to :survey! ! before_create :set_token! ! validates :recipient_email, presence: true, format: EMAIL_REGEX! validates :status, inclusion: { in: STATUSES }! ! def to_param! token! end! ! def deliver! Mailer.invitation_notification(self).deliver! end! ! private! ! def set_token! self.token = SecureRandom.urlsafe_base64! end! end
28. class Invitation < ActiveRecord::Base! EMAIL_REGEX = /\A([^@\s]+)@((:?[a-z0-9]+\.)+[a-z]{2,})\z/i! STATUSES = %w(pending accepted)! ! belongs_to :sender, class_name: 'User'! belongs_to :survey! ! before_create :set_token! ! validates :recipient_email, presence: true, format: EMAIL_REGEX! validates :status, inclusion: { in: STATUSES }! ! def to_param! token! end! ! def deliver! Mailer.invitation_notification(self).deliver! end! ! private! ! def set_token! self.token = SecureRandom.urlsafe_base64! end! end
29. class Invitation < ActiveRecord::Base! EMAIL_REGEX = /\A([^@\s]+)@((:?[a-z0-9]+\.)+[a-z]{2,})\z/i! STATUSES = %w(pending accepted)! ! belongs_to :sender, class_name: 'User'! belongs_to :survey! ! before_create :set_token! ! validates :recipient_email, presence: true, format: EMAIL_REGEX! validates :status, inclusion: { in: STATUSES }! ! def to_param! token! end! ! def deliver! Mailer.invitation_notification(self).deliver! end! ! private! ! def set_token! self.token = SecureRandom.urlsafe_base64! end! end
30. class Invitation < ActiveRecord::Base! EMAIL_REGEX = /\A([^@\s]+)@((:?[a-z0-9]+\.)+[a-z]{2,})\z/i! STATUSES = %w(pending accepted)! ! belongs_to :sender, class_name: 'User'! belongs_to :survey! ! before_create :set_token! ! validates :recipient_email, presence: true, format: EMAIL_REGEX! validates :status, inclusion: { in: STATUSES }! ! def to_param! token! end! ! def deliver! Mailer.invitation_notification(self).deliver! end! ! private! ! def set_token! self.token = SecureRandom.urlsafe_base64! end! end
31. class Invitation < ActiveRecord::Base! EMAIL_REGEX = /\A([^@\s]+)@((:?[a-z0-9]+\.)+[a-z]{2,})\z/i! STATUSES = %w(pending accepted)! ! belongs_to :sender, class_name: 'User'! belongs_to :survey! ! before_create :set_token! ! validates :recipient_email, presence: true, format: EMAIL_REGEX! validates :status, inclusion: { in: STATUSES }! ! def to_param! token! end! ! def deliver! Mailer.invitation_notification(self).deliver! end! ! private! ! def set_token! self.token = SecureRandom.urlsafe_base64! end! end
32. S
    O
    L
    I
    D
33. S
    O
    L
    I
    D pen closed
34. # does not follow OCP! class Purchase! def charge_user!! Stripe.charge(user: user, amount: amount)! end! end
35. # does not follow OCP! class Purchase! def charge_user!! Stripe.charge(user: user, amount: amount)! end! end # follows OCP by depending on an abstraction! class Purchase! def charge_user!(payment_processor)! payment_processor.charge(user: user, amount: amount)! end! end
36. class Printer! def initialize(item)! @item = item! end! ! def print! thing_to_print = case @item! when Text! @item.to_s! when Image! @item.filename! when Document! @item.formatted! end! ! send_to_printer(thing_to_print)! end! end
37. class Printer! def initialize(item)! @item = item! end! ! def print! send_to_printer(@item.printable_representation)! end! end Dependency Injection
38. # does not follow OCP! class Unsubscriber! def unsubscribe!! SubscriptionCanceller.new(user).process! CancellationNotifier.new(user).notify! CampfireNotifier.announce_sad_news(user)! end! end
39. class UnsubscriptionCompositeObserver! def initialize(observers)! @observers = observers! end! ! def notify(user)! @observers.each do |observer|! observer.notify(user)! end! end! end! ! class Unsubscriber! def initialize(observer)! @observer = observer! end! ! def unsubscribe!(user)! observer.notify(user)! end! end Composite Pattern
40. class UnsubscriptionCompositeObserver! def initialize(observers)! @observers = observers! end! ! def notify(user)! @observers.each do |observer|! observer.notify(user)! end! end! end! ! class Unsubscriber! def initialize(observer)! @observer = observer! end! ! def unsubscribe!(user)! observer.notify(user)! end! end Observer Pattern
41. class UnsubscriptionCompositeObserver! def initialize(observers)! @observers = observers! end! ! def notify(user)! @observers.each do |observer|! observer.notify(user)! end! end! end! ! class Unsubscriber! def initialize(observer)! @observer = observer! end! ! def unsubscribe!(user)! observer.notify(user)! end! end
42. A word of caution
43. S
    O
    L
    I
    D
44. S
    O
    L
    I
    D iskov substitution
45. Let q(x) be a property provable about objects x of type T. Then q(y) should be provable for objects y of type S where S is a subtype of T. “
46. blah q(x) blah blah blah blah blah blah blah blah x blah T. Blah q(y) blah blah blah blah blah blah y blah blah S blah S blah blah blah blah T. “
47. class Signup! def initialize(attributes)! @attributes = attributes! end! ! def save! account = Account.create!(@attributes[:account])! account.users.create!(@attributes)! end! end! ! class SignupsController < ApplicationController! def create! build_signup.save! end! ! def build_signup! Signup.new(params[:signup])! end! end
49. A wild requirement appears…
50. class InvitationSignup < Signup! def save(invitation)! user = super! invitation.accept(user)! user! end! end A wild requirement appears…
51. class SignupsController < ApplicationController! def create! signup = build_signup! if params[:invitation_id]! invitation = Invitation.find(params[:invitation_id])! signup.save(invitation)! else! signup.save! end! end! ! def build_signup! if params[:invitation_id]! InvitationSignup.new(params[:signup])! else! Signup.new(params[:signup])! end! end! end
52. class SignupsController < ApplicationController! def create! signup = build_signup! if params[:invitation_id]! invitation = Invitation.find(params[:invitation_id])! signup.save(invitation)! else! signup.save! end! end! ! def build_signup! if params[:invitation_id]! InvitationSignup.new(params[:signup])! else! Signup.new(params[:signup])! end! end! end
53. def InvitationSignup < Signup! def initialize(attributes, invitation)! super(attributes)! @invitation = invitation! end! ! def save! user = super! @invitation.accept(user)! user! end! end The public API remains the same
54. class SignupsController < ApplicationController! def create! build_signup.save! end! ! def build_signup! if params[:invitation_id]! InvitationSignup.new(params[:signup])! else! Signup.new(params[:signup])! end! end! end
55. S
    O
    L
    I
    D
56. S
    O
    L
    I
    D nterface segragation
57. public class WebPage implements IWebPage {! public String currentUrl() {};! public void setUrl(String url) {};! public String[] consoleMessages() {};! public String[] alertMessages() {};! public String[] confirmMessages() {};! public String[] promptMessages() {};! }
58. public class WebPage implements IWebPage {! public String currentUrl() {};! public void setUrl(String url) {};! public String[] consoleMessages() {};! public String[] alertMessages() {};! public String[] confirmMessages() {};! public String[] promptMessages() {};! } Not all methods are related
59. public class VisitCommand {! public VisitCommand(WebPage page, String url) {! this.page = page;! this.url = url;! }! ! public void start() {! page.setUrl(url)! }! ! private WebPage page;! private String url;! } Command Pattern
60. public interface HasUrl {! public String currentUrl() {};! public void setUrl(String url) {};! }! ! public interface HasMessages {! public String[] consoleMessages() {};! public String[] alertMessages() {};! public String[] confirmMessages() {};! public String[] promptMessages() {};! } public class WebPage implements HasUrl, HasMessages {
61. public class VisitCommand {! public VisitCommand(HasUrl page, String url) {! this.page = page;! this.url = url;! }! ! public void start() {! page.setUrl(url)! }! ! private HasUrl page;! private String url;! }
62. public class VisitCommand {! public VisitCommand(HasUrl page, String url) {! this.page = page;! this.url = url;! }! ! public void start() {! page.setUrl(url)! }! ! private HasUrl page;! private String url;! }
63. http://tenderlovemaking.com/2014/06/02/yagni-methods-are-killing-me.html loop do params[:foo] params.delete :foo params[:foo] = [Object.new] end def convert_value_to_parameters(value) if value.is_a?(Array) && !converted_arrays.member?(value) converted = value.map { |_| convert_value_to_parameters(_) } converted_arrays << converted converted elsif value.is_a?(Parameters) || !value.is_a?(Hash) value else self.class.new(value) end end
64. merge! delete_if keep_if select! reject!
65. S
    O
    L
    I
    D
66. S
    O
    L
    I
    Dependency inversion
67. “High level modules should not depend on low level modules, they should both depend on abstractions
68. #Violates DIP! class Copier! def self.copy! reader = KeyboardReader.new! writer = Printer.new! ! keystrokes = reader.read_until_eof! writer.write(keystrokes)! end! end
69. #Obeys DIP. Is decoupled and reusable.! class Copier! def initialize(reader, writer)! @reader = reader! @writer = writer! end! ! def copy! keystrokes = @reader.read_until_eof! @writer.write(keystrokes)! end! end! ! Copier.new(KeyboardReader.new, Printer.new)! Copier.new(KeyboardReader.new, NetworkPrinter.new)
70. class NetworkPrinterAdapter! def initialize(network_printer)! @network_printer = network_printer! end! ! def write(keystrokes)! @network_printer.print(keystrokes)! end! end! ! network_printer = ! NetworkPrinterAdapter.new(NetworkPrinter.new)! Copier.new(KeyboardReader.new, network_printer) Adapter Pattern
71. class Product < ActiveRecord::Base! has_many :purchases! end! ! class Purchase < ActiveRecord::Base! belongs_to :Product! ! def has_receipt?! receipt.present?! end! ! def receipt_id! receipt.id! end! ! def receipt_address! receipt.details.address! end! ! private! ! def receipt! Stripe::Receipt.find(stripe_order_id)! end! end
72. class PurchaseWithReceipt < SimpleDelegator! def initialize(purchase, receipt_finder)! super(purchase)! @receipt_finder = receipt_finder! end! ! def has_receipt?! receipt.present?! end! ! def receipt_id! receipt.id! end! ! def receipt_address! receipt.details.address! end! ! private! ! def receipt! @receipt_finder.find(stripe_order_id)! end! end class Product < ActiveRecord::Base! has_many :purchases! end! ! class Purchase < ActiveRecord::Base! belongs_to :product! end
73. S
    O
    L
    I
    D ingle responsibility pen closed iskov substitution nterface segragation ependency inversion Uncle Bob Martin
74. RECAP DESIGN PRINCIPLES DESIGN PATTERNS + = CLEAN CODE
75. Code Smells Sir, your issues have some code.
76. long method Smell number 1
78. Can’t tell what it does at a glance, it’s
79. Can’t tell what it does at a glance, it’s TOO LONG
80. Can’t tell what it does at a glance, it’s TOO LONG More than one level of nesting, probably
81. Can’t tell what it does at a glance, it’s TOO LONG More than one level of nesting, probably TOO LONG
82. Can’t tell what it does at a glance, it’s TOO LONG More than one level of nesting, probably TOO LONG More than one level of abstraction, may be
83. Can’t tell what it does at a glance, it’s TOO LONG More than one level of nesting, probably TOO LONG TOO LONG More than one level of abstraction, may be
84. Can’t tell what it does at a glance, it’s TOO LONG More than one level of nesting, probably TOO LONG TOO LONG More than one level of abstraction, may be More than 5 lines
85. Can’t tell what it does at a glance, it’s TOO LONG More than one level of nesting, probably TOO LONG TOO LONG More than one level of abstraction, may be More than 5 lines TOO LONG
86. Can’t tell what it does at a glance, it’s TOO LONG More than one level of nesting, probably TOO LONG TOO LONG More than one level of abstraction, may be More than 5 lines TOO LONG REFACTOR
87. Extract Method: Split method into many auxiliary methods Solution #1
88. Replace temp with query: Move local variables into methods Solution #2
89. large class Smell number 2
91. Need to scroll to know what it does, it’s
92. Need to scroll to know what it does, it’s TOO BIG
93. Need to scroll to know what it does, it’s TOO BIG More private methods than public, it’s
94. Need to scroll to know what it does, it’s TOO BIG More private methods than public, it’s TOO BIG
95. Need to scroll to know what it does, it’s TOO BIG More private methods than public, it’s TOO BIG More than seven methods, probably
96. Need to scroll to know what it does, it’s TOO BIG More private methods than public, it’s TOO BIG TOO BIG More than seven methods, probably
97. Need to scroll to know what it does, it’s TOO BIG More private methods than public, it’s TOO BIG TOO BIG More than seven methods, probably More than 100 lines
98. Need to scroll to know what it does, it’s TOO BIG More private methods than public, it’s TOO BIG TOO BIG More than seven methods, probably More than 100 lines TOO BIG
99. Need to scroll to know what it does, it’s TOO BIG More private methods than public, it’s TOO BIG TOO BIG More than seven methods, probably More than 100 lines TOO BIG REFACTOR
100. Extract class: If the class has multiple responsibilities Solution #1
101. Extract decorator: If the class has many objects related to a single action Solution #2
102. class Report def initialize @title = 'Monthly Report' @text = [ 'Things are going', 'really, really well.' ] end ! def output_report ...HTML specific stuff... end end strategy pattern: reports
103. bad code class Report def initialize @title = 'Monthly Report' @text = [ 'Things are going', 'really, really well.' ] end ! def output_report ...HTML specific stuff... end end strategy pattern: reports
104. class Report def initialize(formatter) @title = 'Monthly Report' @text = [ 'Things are going', 'really, really well.' ] @formatter = formatter.new(@title, @text) end ! def formatter=(formatter) @formatter = formatter.new(@title, @text) end ! def output_report @formatter.output_report end end strategy pattern: reports
105. class Report def initialize(formatter) @title = 'Monthly Report' @text = [ 'Things are going', 'really, really well.' ] @formatter = formatter.new(@title, @text) end ! def formatter=(formatter) @formatter = formatter.new(@title, @text) end ! def output_report @formatter.output_report end end better code strategy pattern: reports
106. strategy pattern: reports report = Report.new(HTMLFormatter) report.output_report ! report.formatter = PlainTextFormatter report.output_report
107. beware of the god class
108. feature envy Smell number 3 All your features are mine
109. Smelling feature envy: 4SYMPTOMS
110. Smelling feature envy: Many references to the same object
111. Smelling feature envy: Local variables or params that are used more than instance variables and methods
112. Smelling feature envy: Methods that include a class name in their name
113. Smelling feature envy: Private methods on the same class with the same parameter
114. Smelling feature envy: class Completion! def score! answers.inject(0) do |result, answer|! question = answer.question! result + question.score(answer.text)! end! end! end
115. Extract method: If possible move part of a method to the appropriate class Solution #1
116. Move method: Move the entire method into the right class Solution #2
117. Solving feature envy: class Answer! def score! question.score(text)! end! end! ! class Completion! answers.inject(0) do |result, answer|! result + answer.score! end! end
118. DESIGN PRINCIPLES DESIGN PATTERNS + = CLEAN CODE
119. missing some style
120. Learn the principles patterns Know the use the smells
121. BLEEDING EDGE
122. Hexagonal Architecture Domain Driven Design (DDD) Presenters Service Objects Value Objects and Immutability Behavior Driven Development (BDD) Object Composition vs Inheritance
123. Practical Object-Oriented Design in Ruby
124. Practical Object-Oriented Design in Ruby Growing Object-Oriented Software
125. Practical Object-Oriented Design in Ruby Growing Object-Oriented Software Test-Driven Development
126. Practical Object-Oriented Design in Ruby Growing Object-Oriented Software Test-Driven Development Clean Code
127. thanks!