Refactoring iOS Projects - Ukraine

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Рефакторинг ! Проектів Refactoring ! Projects @akosma – @uaMobiTech – July 16th 2016 © akosma 2016 1

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Рефакторинг !⌚#$ Проектів Refactoring !⌚#$ Projects @akosma – @uaMobiTech – July 16th 2016 © akosma 2016 2

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Thank you ! More information at developer.apple.com © akosma 2016 5

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Sorry! ! © akosma 2016 7

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Thank you ! More information at jetbrains.com/objc © akosma 2016 10

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Seriously? ! © akosma 2016 12

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Live and Let IDE ! © akosma 2016 13

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Big Topic ! © akosma 2016 14

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More ! © akosma 2016 16

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Yeah baby !" © akosma 2016 18

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What is it? ! © akosma 2016 20

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Refactoring (noun): a change made to the internal structure of software to make it easier to understand and cheaper to modify without changing its observable behavior. © akosma 2016 21

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Why to? ! © akosma 2016 22

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—To improve the design of software —To make it easier to understand —To make it easier to ﬁnd and ﬁx bugs —To program faster —To annoy your manager © akosma 2016 23

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When to? ⏰ © akosma 2016 24

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—When you add features —When ﬁxing bugs —During code reviews © akosma 2016 25

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When not to? ⛔ © akosma 2016 26

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1. Add Tests 2. Refactor © akosma 2016 28

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How to? ! © akosma 2016 31

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Bad Smells !68 —Duplicated code —Long methods —Large class —Long parameter list —Divergent change —Shotgun surgery —Feature envy —Data clumps —Primitive obsession —Switch statements —Parallel inheritance hierarchies —Lazy class —Speculative generality —Temporary ﬁeld —Message chains —Middle Man —Inappropriate intimacy —Alternative classes with diﬀerent interfaces —Incomplete library class —Data class —Refused bequest —Comments 68 Source: “Refactoring” by Martin Fowler (1999) © akosma 2016 32

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!⌚#$ Speciﬁc Smells ! Swift and Cocoa Smells ! Class Design Smells ! Project Management Smells © akosma 2016 33

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! Swift and Cocoa Smells © akosma 2016 34

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!" SwiftyLeaks © akosma 2016 35

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Memory Leaks in Swift Reference Cycles23: —Instances —Closures 23 Source: Apple Developer Library © akosma 2016 37

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Instance Reference Cycles (1/2) class Person { let name: String var apartment: Apartment? } class Apartment { let unit: String var tenant: Person? // Ouch! } © akosma 2016 38

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Instance Reference Cycles (2/2) class Person { let name: String var apartment: Apartment? } class Apartment { let unit: String weak var tenant: Person? // Yay! } © akosma 2016 40

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weak vs. unowned —weak can be nil —unowned cannot be nil —unowned ➡ always nonoptional types © akosma 2016 42

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Closure Reference Cycles (1/2) let obj = SomeObject() obj.blockMember = { return obj.property // Ouch! } © akosma 2016 43

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Closure Reference Cycles (2/2) let obj = SomeObject() obj.blockMember = { [unowned obj] return obj.property // Yay! } © akosma 2016 44

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Closures are reference types⾠ © akosma 2016 45

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!" Hungarian Notation © akosma 2016 46

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protocol IUnknown { func QueryInterface (_ riid: REFIID, _ ppvObject: LPVOID) -> HRESULT func AddRef() -> ULONG func Release() -> ULONG } protocol IDispatch : IUnknown { func GetTypeInfoCount(pctinfo: UInt) -> HRESULT func GetTypeInfo(_ iTInfo: UInt, _ lcid: LCID, _ ppTInfo: ITypeInfo) -> HRESULT func GetIDsOfNames(_ riid: REFIID, _ rgszNames: OLECHAR, _ cNames: UInt, _ lcid: LCID, _ rgDispId: DISPID) -> HRESULT func Invoke(_ dispIdMember: DISPID, _ riid: REFIID, _ lcid: LCID, _ wFlags: WORD, _ pDispParams: DISPPARAMS, _ pVarResult: VARIANT, _ pExcepInfo: EXCEPINFO, _ puArgErr: UInt32) -> HRESULT } © akosma 2016 47

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let oPerson = Server.CreateObject("Person") var bBusy = true if (bBusy) { bBusy = false let riid = CFUUIDGetUUIDBytes(CFUUIDCreate(kCFAllocatorDefault)) let ppvObject = UnsafeMutablePointer(allocatingCapacity: 10) let result = oPerson.QueryInterface(riid, ppvObject) if result == 0x80090032 { bBusy = true oPerson.Invoke(0, riid, riid, 0, riid, nil, nil, 0) } } © akosma 2016 48

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Programs must be written for people to read, and only incidentally for machines to execute. © akosma 2016 49

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Swift API design guidelines55 // Make APIs read grammatically friends.remove(ted) mainView.addChild(button, at: origin) truck.removeBoxes(withLabel: "uaMobiTech") // Use verbs for side effects friends.reverse() viewController.present(animated: true) 55 Source: WWDC 2016 session 403 © akosma 2016 50

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Swift API design guidelines55 // Use nouns for returned values button.backgroundTitle(for: .disabled) friends.suffix(3) // Mutating and non-mutating method pairs x.reverse() // mutating let y = x.reversed() // non-mutating dir.appendPathComponent(".txt") // mutating let newDir = dir.appendingPathComponent(".txt") // non-mutating 55 Source: WWDC 2016 session 403 © akosma 2016 51

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Swift 㲗 Objective-C Two diﬀerent signatures: one for Swift, another for Objective-C @objc() exports Swift API ➡ Objective-C NS_SWIFT_NAME() Objective-C APIs ➡ Swift © akosma 2016 52

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!" Objective-C Nostalgia © akosma 2016 53

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Migrate to Swift3 NS_ASSUME_NONNULL_BEGIN #define let __auto_type const #define var __auto_type @property(nonatomic, nonnull, copy) NSString *name; @property(nonatomic, nullable, weak) id delegate; - (nullable NSArray *)arrayWithWord:(nonnull NSString *)word { // NSArray * _Nonnull words = @[@"one", @"two", word]; __auto_type _Nonnull words = @[@"one", @"two", word]; return words; } NS_ASSUME_NONNULL_END 3 Source: Swift Blog © akosma 2016 54

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Caveats —Objective-C cannot subclass a Swift class —…unless marked @objc —Tuples, Swift enums and structs are not accessible from Objective-C. © akosma 2016 55

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!" Homemade Cache © akosma 2016 56

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“There are only two hard things in Computer Science: cache invalidation and naming things.” Phil Karlton10 10 Source: Martin Fowler © akosma 2016 57

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NSURLCache let config = URLSessionConfiguration.default config.requestCachePolicy = .returnCacheDataElseLoad let memoryCapacity = 10 * 1024 * 1024; let diskCapacity = 20 * 1024 * 1024; let cache = URLCache(memoryCapacity: memoryCapacity, diskCapacity: diskCapacity, diskPath: nil) URLCache.shared = cache © akosma 2016 58

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!" Tagged Views © akosma 2016 59

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Do not viewWithTag() override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell { let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) let object = objects[indexPath.row] as! NSDate cell.textLabel!.text = object.description let switchControl = cell.viewWithTag(1) as! UISwitch // Ouch! switchControl.setOn(false, animated: false) return cell } © akosma 2016 60

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Custom View Class override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell { let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) as! CustomViewCell let object = objects[indexPath.row] as! NSDate cell.titleLabel.text = object.description cell.switchControl.setOn(true, animated: false) // Yay! return cell } © akosma 2016 61

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!" Illicit Association © akosma 2016 62

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Associated Objects 86 extension NSWhatever { private struct Keys { static var Value = "AssociatedValue" } var associatedString: String? { get { return objc_getAssociatedObject(self, &Keys.Value) as? String } set { objc_setAssociatedObject(self, &Keys.Value, newValue as NSString?, .OBJC_ASSOCIATION_COPY_NONATOMIC) } } } var obj = NSWhatever() obj.associatedString = "Some other string" 86 Source: NSHipster © akosma 2016 63

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Associated Objects 14 Do not if you can use instead: —Subclassing —Target-Action —Gesture recognizers —Delegation —NSNotiﬁcation 14 Source: NSHipster © akosma 2016 64

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! Class Design Smells © akosma 2016 66

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!" Class Struggle © akosma 2016 67

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class or struct? ! (1/2) protocol Modifiable { // protocols FTW! var value : Int { get set } mutating func increase() } extension Modifiable { mutating func increase() { value += 100 } } © akosma 2016 68

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class or struct? ! (2/2) struct TypeOne : Modifiable { var value = 0 } class TypeTwo : Modifiable { var value = 0 } var v1, v2, r1, r2 : Modifiable v1 = TypeOne(); v2 = v1 // Value type, copied r1 = TypeTwo(); r2 = r1 // Reference type, not copied v2.increase(); assert(v1.value != v2.value) r2.increase(); assert(r1.value == r2.value) © akosma 2016 69

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Reference Types ! —Inheritance —Reference semantics —Use Swift types in Objective-C Value Types ! —Always implement Equatable on your own76 —More testable architectures —Immutable by default 76 Source: WWDC 2015 Session 414 © akosma 2016 70

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!" Massive View Controller (MVC) and Massive App Delegate (MAD) © akosma 2016 71

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Class Breakdown ! Maximum 400 lines ! © akosma 2016 73

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Empty States72 1. First use39 2. User cleared 3. Errors 39 Source: Designing For The Empty States 72 Source: emptystat.es © akosma 2016 74

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State Machines12 —AppState enumeration with associated lambdas —GKState and GKStateMachine Other Approaches —Model-View-ViewModel (MVVM) —Protocols & Extensions —Dependency Injection —ReSwift, PromiseKit, RxSwift, ReactKit, ReactiveCocoa… 12 Source: Github © akosma 2016 75

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AppState (1/3) enum AppState { case None case Active(action: Block) // typealias Block = (Void) -> Void case Inactive(action: Block) func execute() { switch self { case .Active(let block): block() case .Inactive(let block): block() default: return } } } © akosma 2016 76

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AppState (2/3) class SomeController { var state = AppState.None { didSet { state.execute() } } func viewDidLoad() { // ... } © akosma 2016 77

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AppState (3/3) func viewDidLoad() { super.viewDidLoad() let inactive = AppState.Inactive { [unowned self] () in self.view.backgroundColor = UIColor.red() } let active = AppState.Active { [unowned self] () in self.view.backgroundColor = UIColor.green() } // ... self.state = inactive } © akosma 2016 78

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GKState and GKStateMachine (1/2) import GameplayKit class ActiveState: GKState { override func isValidNextState(_ stateClass: AnyClass) -> Bool { if stateClass == InactiveState.self { return true } return false } override func didEnter(withPreviousState previousState: GKState?) { // change UI elements, etc, etc... } override func willExit(withNextState nextState: GKState) { // ... } } © akosma 2016 79

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GKState and GKStateMachine (2/2) let active = ActiveState() let inactive = InactiveState() let stateMachine = GKStateMachine(states: [active, inactive]) stateMachine.enterState(InactiveState.self) © akosma 2016 80

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Model – View – ViewModel (MVVM 1/2) class DetailViewModel: NSObject { let model : Model init(withModel model: Model) { self.model = model } var displayText : String { return self.model.description } } © akosma 2016 82

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Model – View – ViewModel (MVVM 2/2) class DetailViewController: UIViewController { @IBOutlet weak var label: UILabel! var viewModel : DetailViewModel? override func viewDidLoad() { super.viewDidLoad() self.label.text = self.viewModel?.displayText } } © akosma 2016 83

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Martin Fowler Says68 —Extract Class (149) —Extract Subclass (330) —Extract Interface (341) —Duplicate Observed Data (189) 68 Source: “Refactoring” by Martin Fowler (1999) © akosma 2016 84

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!" Forgotten Memory Warnings © akosma 2016 85

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Memory Warnings func applicationDidReceiveMemoryWarning(_ application: UIApplication) { // ... on the app delegate... } override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning() // ... on every controller... } // ... and anywhere else let center = NotificationCenter.default() let notification = NSNotification.Name.UIApplicationDidReceiveMemoryWarning let selector = #selector(SomeClass.handler(_:)) center.addObserver(self, selector: selector, name: notification, object: nil) © akosma 2016 86

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Lazy Loading Class class LazyLoader { var _backingField: String? var property: String? { get { if _backingField == nil { _backingField = "text" } return _backingField } set { _backingField = newValue } } } © akosma 2016 87

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!" Long Switch Statement © akosma 2016 88

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Pattern Matching44 switch (indexPath.section, indexPath.row) { case (0, let row): cell.backgroundColor = UIColor.lightGray() // ... case (let section, 0) where section % 2 == 0: cell.backgroundColor = UIColor.brown() // ... case let (3, row) where validate(row): cell.backgroundColor = UIColor.blue() // ... default: cell.backgroundColor = UIColor.white() } 44 Source: Ash Furrow © akosma 2016 89

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Martin Fowler Says68 —Extract Method (110) —Move Method (142) —Replace Type Code With Subclasses (223) —Replace Type Code With State/Strategy (227) —Replace Conditional with Polymorphism (255) 68 Source: “Refactoring” by Martin Fowler (1999) © akosma 2016 90

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!" Long Method Names © akosma 2016 91

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“There are only two hard things in Computer Science: cache invalidation and naming things.” Phil Karlton10 10 Source: Martin Fowler © akosma 2016 92

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Cocoa Awards™ ! © akosma 2016 93

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Cocoa Awards™ ! Longest Method Name Category95 95 Source: Quora and Github © akosma 2016 94

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…and the winner is… // QCPlugInContext class - (id) outputImageProviderFromBufferWithPixelFormat:(NSString*)format pixelsWide:(NSUInteger)width pixelsHigh:(NSUInteger)height baseAddress:(const void*)baseAddress bytesPerRow:(NSUInteger)rowBytes releaseCallback:(QCPlugInBufferReleaseCallback)callback releaseContext:(void*)context colorSpace:(CGColorSpaceRef)colorSpace shouldColorMatch:(BOOL)colorMatch; © akosma 2016 95

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Martin Fowler Says68 —Replace Parameter with Method (292) —Preserve Whole Object (288) —Introduce Parameter Object (295) 68 Source: “Refactoring” by Martin Fowler (1999) © akosma 2016 97

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Parameter Objects in Cocoa // Map snapshots let options = MKMapSnapshotOptions() options.region = mapView.region options.size = mapView.frame.size let snapshotter = MKMapSnapshotter(options: options) // URL Sessions let config = URLSessionConfiguration() config.httpShouldSetCookies = false config.timeoutIntervalForRequest = 2.0 let session = URLSession(configuration: config) © akosma 2016 98

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Excessive User Interface Idiom Checks // Only if you need compatibility with iPhone OS 3.2... really? if UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiom.pad { // ... iPad-only code } let idiom = UIDevice.current().userInterfaceIdiom if idiom == UIUserInterfaceIdiom.phone { // ... iPhone-only code } © akosma 2016 100

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Excessive OS Version Checks46 let ver = OperatingSystemVersion(majorVersion: 10, minorVersion: 0, patchVersion: 0) if ProcessInfo().isOperatingSystemAtLeast(ver) { ... } let os = ProcessInfo().operatingSystemVersion switch (os.majorVersion, os.minorVersion, os.patchVersion) { case (10, _, _): print("iOS >= 10.0.0") default: print("Previous versions") } 46 Source: NSHipster © akosma 2016 101

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Behave Appropriately 1. Encapsulate features into subclasses 2. Last resort: check feature existence if let feature = NSClassFromString("INIntent") { print("Intents.framework (SiriKit) available") } © akosma 2016 102

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Extensions Explosion —19 iOS extensions —11 macOS extensions Check out Apple’s “Lister” application!99 99 Source: Apple Developer Library © akosma 2016 110

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Conventions for Xcode28 —Create folders for each platform: iOS, macOS, watchOS, tvOS —Target folders inside platform folders —Shared folder for cross-platform ﬁles —Separate items into Assets and Source directories 28 Source: The.Swift.Dev © akosma 2016 111

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Cocoapods Best Practices —Check in Pods folder, Podfile and Podfile.lock. —pod outdated in a separate branch once a week —Use rbenv to control Ruby installations —Team uses the same version of Cocoapods © akosma 2016 113

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Specify Pod Versions ✔ target 'MyApp' do pod 'AFNetworking', '~> 3.0' pod 'FBSDKCoreKit', '~> 4.9' end ➡ Choose your pods wisely! © akosma 2016 114

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Problem —Controllers tied to Storyboard ➡ hard to reuse —Merge conﬂicts —Slow loading —Complex navigation © akosma 2016 122

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Solution —Use storyboards only for navigation —Use XIB ﬁles only for UI design Steps: 1. Menu Editor -> Refactor to Storyboard… 2. ViewController.swift + ViewController.xib 3. Remove view outlet from Storyboard in Controller © akosma 2016 123

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// Instantiating through the Storyboard if let controller = self.storyboard?.instantiateViewController(withIdentifier: "Ctrl") { // ... } // Instantiating manually // This constructor automatically loads XIB file let controller = ViewController() © akosma 2016 126

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Common Backend API Sins —SOAP, XML-RPC —Chatty design —Lack of Control —QOS, Security, Performance… ! " ↩ # © akosma 2016 131

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! Swift and Cocoa Smells ! SwiftyLeaks " Hungarian Notation # Objective-C Nostalgia $ Homemade Cache % Tagged View & Illicit Association © akosma 2016 135

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! Class Design Smells ! Class Struggle " Massive View Controller & App Delegate # Forgotten Memory Warnings $ Long Switch Statement % Long Method Names & Excessive Curiosity © akosma 2016 136

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! Project Management Smells ! Invisible Documentation " Folder Clusterfuck # Cocoapods Galore $ Rogue Compiler Warnings % User Discrimination & Interface Builder Attack ' iOS Nostalgia ( Backend API Anarchy © akosma 2016 137

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Got More Smells? Call to action! 1. Give smells a cool name and a description 2. Specify the refactoring 3. Share! © akosma 2016 138