Nuke it from Orbit: How to fix Massive View Controller Once and for All

Everyone knows that MVC done badly inevitably leads to massive view controllers, but it doesn't need to be that way. In this talk you'll learn how design patterns from Cocoa Touch and how Swift can help you simplify your code, reduce coupling, and make your maintenance easier.

Transcript

1. PAUL HUDSON — @twostraws NUKE IT FROM ORBIT:
 How to Fix Massive View
 Controller Once and for All https://www.hackingwithswift.com
2. HACKING WITH SWIFT
6. ▸ @twostraws on Twitter ▸ twostraws on GitHub ▸ twostraws on Reddit ▸ twostraws on StackOverflow ▸ paul@hackingwithswift.com GET IN TOUCH!
7. NUKE IT FROM ORBIT How to fix massive view controllers
 once and for all
10. SITE SAFETY days since
 the last talk on
 iOS architectures 0
11. It is a truth universally acknowledged that every good iOS conference must be 
 in want of a talk on
 app architectures. Jane Austen (Probably)
12. I can fix MVC and
 so can my wife!
14. ▸ What’s the problem? ▸ What are the alternatives? ▸ How to fix MVC ▸ Lots of code to read THE PLAN
15. “I’m sorry, I can’t hear you over the sound of how awesome I am.”
16. CODE OR IT DIDN’T HAPPEN
17. ▸ What’s the problem? ▸ What are the alternatives? ▸ How to fix ▸ Lots of code to read THE PLAN MVC
18. MVC
20. WHAT’S THE PROBLEM?
22. MVC MASSIVE VIEW CONTROLLER
24. Model View Controller Networking Business logic Data storage Delegation
25. Controller Networking Business logic Data storage Delegation Model View
26. Animations I/O Segues Lifecycle Events Kitchen Sink
30. Paris 2018
31. Paris 2018
32. Paris 2018
35. “When you call something a Controller, it absolves you of the need to separate your concerns. Nothing is out of scope, since its purpose is to control things. Boundless, it begins absorbing responsibilities.” Soroush Khanlou @khanlou
36. cellForRowAt
37. Fetch model data Create table view cell Render cell Format model data Lay out cell with formatted data
38. Fetch model data Create table view cell Render cell Format model data Lay out cell with formatted data
41. Your tests shall not pass!
43. WHAT ARE THE ALTERNATIVES?
44. MVC VIP MVVM MVVM-C VIPER
47. That’s not an architecture… …THIS is an architecture!
48. Guilherme Rambo @_inside https://iosarchitecture.top
50. MVC VIP MVVM-C VIPER MVVM
51. Controller Networking Business logic Data storage Delegation Model View UIViewController
52. ViewModel Networking Business logic Data storage Delegation Model View UIViewController
53. ViewModel Networking Business logic Data storage Delegation Model View UIViewController
54. ViewModel Networking Business logic Data storage Delegation import UIKit
55. ViewModel Networking Business logic Data storage Delegation import UIKit
56. Networking Business logic Data storage Delegation Segues Animations I/O Memes
59. • Person A: “No Scotsman puts sugar on his porridge.” • Person B: “But my uncle Angus likes sugar with his porridge.” • Person A: “Ah yes, but no true Scotsman puts sugar on his porridge.”
60. • Person A: “MVC architecture neatly separates models, views, and controllers.” • Person B: “But all these apps put view code into the controller.” • Person A: “Ah yes, but that’s not a true MVC architecture.”
61. Architecture not working for you? You’re holding
 it wrong.
62. > > MVVM MVC
65. ▸ What’s the problem? ▸ What are the alternatives? ▸ How to fix MVC ▸ Lots of code to read THE PLAN
66. ▸ What’s the problem? ▸ What are the alternatives? ▸ How to fix MVC ▸ Lots of code to read THE PLAN
67. MVC
 YOU’RE HOLDING IT WRONG
70. class MegaController: UIViewController, UITableViewDataSource, UITableViewDelegate, UIPickerViewDataSource, UIPickerViewDelegate, UITextFieldDelegate, WKNavigationDelegate, URLSessionDownloadDelegate {
71. “Model, view, and exactly one controller”
72. WKNavigationDelegate
73. if let host = navigationAction.request.url?.host { if allowedSites.contains(where: host.contains) { decisionHandler(.allow); return } } decisionHandler(.cancel) func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) { }
74. import Foundation import WebKit class ChildFriendlyWebDelegate: NSObject, WKNavigationDelegate { var allowedSites = ["apple.com", "google.com"] // paste the delegate code here }
75. MegaController UITableViewDataSource UITableViewDelegate UIPickerViewDataSource UIPickerViewDelegate UITextFieldDelegate URLSessionDownloadDelegate WKNavigationDelegate Not all controllers are view controllers!
76. let childMode = ChildFriendlyWebDelegate() myWebView.navigationDelegate = childMode webView2.navigationDelegate = childMode let unlocked = UnrestrictedWebDelegate() myWebView.navigationDelegate = unlocked
77. View controller is smaller Delegate follows single responsibility More testable?
78. func isAllowed(url: URL?) -> Bool { guard let host = url?.host else { return false } if allowedSites.contains(where: host.contains) { return true } return false }
79. func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) { if isAllowed(url: navigationAction.request.url) { decisionHandler(.allow) } else { decisionHandler(.cancel) } }
80. View controller is smaller Delegate follows single responsibility More testable
84. DO NOT WANT!
85. TMTOWTDI
86. backgroundColor = UIColor(white: 0.9, alpha: 1) let stack = UIStackView() stack.translatesAutoresizingMaskIntoConstraints = false stack.spacing = 10 view.addSubview(stack) stack.topAnchor.constraint(equalTo: func viewDidLoad() {
88. Coder refactors massive view controller with this one weird trick
89. Coder refactors massive view controller with this one weird trick Controller Model View
90. Coder refactors massive view controller with this one weird trick Controller Model View
91. Views are small Views are composeable Views are reusable Dave DeLong @DaveDeLong
92. class ViewController: UIViewController { var shareView = SharePromptView() override func loadView() { view = shareView } }
93. A B C D E F G
95. Wittgenstein’s Ladder
96. A view controller is best thought of as being one screen of information” HACKING WITH SWIFT: PROJECT 1 “
99. Master Detail
101. 1. Call addChildViewController() on your parent view controller, passing in your child. 2. Set the child’s frame to whatever you need, if you’re using frames. 3. Add the child’s view to your main view, along with any Auto Layout constraints. 4. Call didMove(toParentViewController:) on the child, passing in your main view controller.
102. @nonobjc extension UIViewController { func add(_ vc: UIViewController, frame: CGRect? = nil) { addChildViewController(vc) vc.view.frame = someFrame view.addSubview(vc.view) vc.didMove(toParentViewController: self) } }
103. @nonobjc extension UIViewController { func add(_ vc: UIViewController, frame: CGRect? = nil) { addChildViewController(vc) if let frame = frame { vc.view.frame = frame } view.addSubview(vc.view) vc.didMove(toParentViewController: self) } }
104. @nonobjc extension UIViewController { func add(_ vc: UIViewController, frame: CGRect? = nil) { addChildViewController(vc) if let frame = frame { vc.view.frame = frame } view.addSubview(vc.view) vc.didMove(toParentViewController: self) } }
105. @nonobjc extension UIViewController { func remove() { willMove(toParentViewController: nil) view.removeFromSuperview() removeFromParentViewController() } }
106. Peter Steinberger @steipete Adds a closure for doing Auto Layout! Surprises with Swift Extensions
107. Views are small Views are composeable Views are reusable
108. View controllers are small View controllers are composeable View controllers are reusable
112. You need smaller view controllers!
113. NUKE IT FROM ORBIT It’s the only way to be sure
114. I need smaller
 view controllers I need smaller
 view controllers I need smaller
 view controllers I need smaller
 view controllers I need to make
 fresh coffee I need smaller
 view controllers
115. Controller Business logic Delegation Model View UIViewController Networking Data storage
116. Controller Business logic Delegation Model View UIViewController Networking Data storage
118. APP DELEGATE Controller Business logic Delegation Model View UIViewController Networking Data storage
119. *sigh*
122. DO NOT WANT
126. WE SHOULD GET KNEE. PADS. .
128. You are here Moving code around Big Frickin’ Wall You need to be here
129. UIView+Additions.swift extension UIViewController { … } Non-lifecycle code in AppDelegate Non-lifecycle code in UIViewController
130. AppDelegate didFinishLaunchingWithOptions applicationDidEnterBackground willContinueUserActivityWithType performFetchWithCompletionHandler applicationProtectedDataDidBecomeAvailable
131. AppDelegate Handling launch and backgrounding Application Continuity (“Handoff”) Background fetching Managing protected data Opening from shared file or URL
132. UIViewController viewDidLoad() viewWillAppear() viewWillDisappear() traitCollectionDidChange() didReceiveMemoryWarning() applicationFinishedRestoringState()
133. UIViewController Updating views with model data Responding to user input Responding to UI changes Saving and restoring UI state
136. UIViewController Updating views with model data Responding to user input Responding to UI changes Saving and restoring UI state Data sources and delegates? Networking? Navigation?
137. UIViewController Updating views with model data Responding to user input Responding to UI changes Saving and restoring UI state Data sources and delegates Networking? Navigation?
138. UIViewController Updating views with model data Responding to user input Responding to UI changes Saving and restoring UI state Data sources and delegates Networking Navigation?
139. UIViewController Updating views with model data Responding to user input Responding to UI changes Saving and restoring UI state Data sources and delegates Networking Navigation?
140. UIViewController Updating views with model data Responding to user input Responding to UI changes Saving and restoring UI state Data sources and delegates Networking Navigation?
141. FLOW CONTROL Coordinators Host VC OperationQueue
142. Host View Controllers
150. 㿂 㿂 㿂
151. 㿂 㿂 㿂 PROTOCOL
152. 㿂 㿂 㿂 PROTOCOL
155. View controllers are small View controllers are composeable View controllers are reusable
156. Coordinators
157. navigationController?.pushViewController( someVC, animated: true )
158. A ?
159. A B
161. A B
162. A B COORDINATOR
163. A B COORDINATOR PROTOCOL
164. COORDINATOR
165. COUPLING IS THE ENEMY
166. OperationQueue
167. let queue = OperationQueue() for headline in headlines { queue.addOperation { generateThumbnail(for: headline) } } queue.waitUntilAllOperationsAreFinished()
168. let queue = OperationQueue() for headline in headlines { queue.addOperation { generateThumbnail(for: headline) } } queue.waitUntilAllOperationsAreFinished()
169. let queue = OperationQueue() for headline in headlines { queue.addOperation { generateThumbnail(for: headline) } } queue.waitUntilAllOperationsAreFinished()
170. let queue = OperationQueue() for headline in headlines { queue.addOperation { generateThumbnail(for: headline) } } queue.waitUntilAllOperationsAreFinished()
171. secondOperation.addDependency(first)
173. A B C
174. A B C
175. A B C
176. A B C
177. A B C
178. A B C
181. WTF
182. SUMMARY
183. ▸ Massive view controller is real. ▸ We start off on the wrong foot thanks to UIViewController. ▸ VCs absorb many responsibilities. ▸ UI always makes testing harder. ▸ Try to avoid import UIKit WHAT’S THE PROBLEM?
184. ▸ There are many – and that’s OK. ▸ Choose for smart reasons: does it solve problems better than MVC? ▸ MVVM works great, but is “overkill” for simpler apps. ▸ MVC is usually the simplest. WHAT ARE THE ALTERNATIVES?
185. ▸ Get data sources and delegates into separate controllers. ▸ Compose views into new views. ▸ Use view controller containment. ▸ Think where code should go. ▸ Start a fight over networking code. HOW TO FIX MVC
187. khanlou.com davedelong.com
188. @twostraws
189. GAME OVER, MAN.
190. PAUL HUDSON — @twostraws NUKE IT FROM ORBIT:
 How to Fix Massive View
 Controller Once and for All https://www.hackingwithswift.com