Converting Objective-C to Swift

Learn about a lot of issues encountered when converting code to Swift, and about Swift in general.

Transcript

1. Converting Objective-C to Swift David Kobilnyk
2. Swift Types Value Types Reference Types Enums Structs Classes Int Float Array Dictionary String Bool Double
3. Value Types
4. Using Enums Objective-C: UIControlStateNormal ! Swift: UIControlState.Normal or just .Normal
5. Using Enums [self.tableView insertRowsAtIndexPaths: @[indexPath] withRowAnimation: UITableViewRowAnimationAutomatic]; ! self.tableView.insertRowsAtIndexPaths( [indexPath], withRowAnimation: .Automatic)
6. Initializing Structs ! CGPoint p = CGPointMake(12, 64); ! ! let p = CGPoint(x: 12, y: 64)
7. No Implicit Casting float red = (arc4random() % 100) / 100.0; ! ! let red = (arc4random() % 100) / 100.0 'UInt32' is not convertible to 'Int' ! let red = Float(arc4random() % 100) / 100.0 // Ok
8. Arrays ! NSArray *a = @[@"pale ale", @"stella"]; ! ! let a: [String] = ["pale ale", "stella"] // or let a = ["pale ale", "stella"]
9. Mutating an Array ! NSMutableArray *a = @[]; [a addObject:@"hefeweizen"]; ! ! var a = [String]() a.append("hefeweizen") a += ["hefeweizen"]
10. Dictionaries ! NSMutableDictionary *ages = [NSMutableDictionary new]; ! ! var ages: [String: Int] = [String: Int]() var ages = [String: Int]()
11. Dictionaries ages[@"Al"] = [NSNumber numberWithInt:35]; ages[@"Liz"] = [NSNumber numberWithInt:26]; ! ages["Al"] = 35 ages["Liz"] = 26
12. Iterating Dictionaries for (NSString *name in ages) { NSLog(@"%@ is %@", name, [ages objectForKey:name]); } ! for (name, age) in ages { println("\(name) is \(age)") }
13. Value Type Mutability let a = [1, 2] a[0] = 5 '@lvalue $T5' is not identical to 'Int' ! var a = [1, 2] a[0] = 5 // no error
14. Using Classes
15. Mutability of Classes let str1 = NSMutableAttributedString(string:"yo") str1.appendAttributedString(str1) // no error ! var str2 = NSAttributedString(string: "yo") str2.appendAttributedString(str2) ! 'NSAttributedString' does not have a member named 'appendAttributedString'
16. Mutability of Classes let str1 = NSMutableAttributedString(string: "yo") var str2 = NSAttributedString(string: "yo") ! str2 = str1 // no error str1 = str2 ! 'Cannot assign to 'let' value 'str1'
17. Class Initialization [UIColor colorWithRed:0.1 green:0.6 blue:0.3 alpha:1.0]; [[UIColor alloc] initWithRed:0.1 green:0.6 blue:0.3 alpha:1.0]; ! UIColor(red: 0.1, green: 0.6, blue: 0.3, alpha: 1.0)
18. Class-Level Usage ! [UITableViewCell class] ! ! UITableViewCell.self
19. Class-Level Usage [self.tableView registerClass: [UITableViewCell class] forCellReuseIdentifier:@"Cell"]; ! tableView.registerClass(UITableViewCell.self, forCellReuseIdentifier: "Cell")
20. Optionals
21. Nil let a: Int = nil Type 'Int' does not conform to protocol 'NilLiteralConvertible' ! let b: Int? = nil // No error
22. Unwrapping Optionals let a: Int? = 10 println(a) // prints "Optional(10)" println(a!) // prints "10" ! let b: Int? = nil println(b!) // fatal error: unexpectedly found nil while unwrapping an Optional value
23. Unwrapping Optionals var name: String? = "Al" if let unwrappedName = name { println(unwrappedName) } else { println("name is nil") }
24. Unwrapping Optionals var name: String? = "Al" if let name = name { // This is ok println(name) // Using unwrapped 'name' }
25. Mutating Optional Value Types if var unwrappedName = name { unwrappedName.write("bert") // unwrappedName changes to "Albert" // name remains "Al" }
26. Mutating Optional Value Types var unwrappedName = name! unwrappedName.write("bert") // name is still "Al" name!.write("bert") // force unwrap // name is now "Albert" name?.write("bert") // safe unwrap // name is now "Albertbert"
27. Mutating Optional Class Types let v: UIView? = UIView() if let u = v { u.hidden = true } // v is updated as well
28. Mutating Optional Class Types let v: UIView? = UIView() let u = v! u.hidden = true // v is updated as well
29. Checking for Nil var name: String? = "Al" if name { // causes error // … } Type 'String?' does not conform to protocol 'BooleanType.Protocol'
30. Checking for Nil var name: String? = "Al" if name != nil { // … } // No error
31. Checking for Nil var name: String? = "Al" if let _ = name { // … } // No error
32. Building Classes
33. Class Declaration class Food { ! } ! let food = Food()
34. Stored Properties class Food { var name: String } Class 'Food' has no initializers
35. Stored Properties class Food { var name: String init() {} } Error: Property 'self.name' not initialized
36. Designated Inits class Food { var name: String init(name: String) { self.name = name } } var food = Food(name: "hard-boiled egg")
37. Default Values class Food { var name: String = "[Unnamed]" } // No error !
38. Optional Properties class Food { var name: String? } // No error !
39. Designated Inits class Food { var name: String init(name: String) { self.name = name } } var food = Food() !
40. Designated Inits class Food { var name: String init(name: String) { self.name = name } } var food = Food() Missing argument for parameter 'name' in call
41. Convenience Inits class Food { var name: String init(name: String) { self.name = name } convenience init() { self.init(name: "[Unnamed]") } }
42. Inits and Inheritance class RecipeIngredient: Food { ! } ! let ingredient = RecipeIngredient()
43. Inits and Inheritance class RecipeIngredient: Food { var quantity: Int } Error: Class ‘RecipeIngredient’ has no initializers
44. Inits and Inheritance class RecipeIngredient: Food { var quantity: Int init(name: String, quantity: Int) { self.quantity = quantity super.init(name: name) } } // No error
45. Inits and Inheritance let ingredient = RecipeIngredient(name: "spinach")
46. Inits and Inheritance let ingredient = RecipeIngredient(name: "spinach") Missing argument for parameter 'quantity' in call
47. Inits and Inheritance class RecipeIngredient: Food { var quantity: Int init(name: String, quantity: Int) { … } override convenience init(name: String) { self.init(name: name, quantity: 1) } }
48. Init Code Conversion Example @interface BNRDrawView () <UIGestureRecognizerDelegate> ! @property (nonatomic, strong) UIPanGestureRecognizer *moveRecognizer; ! @end
49. Init Code Conversion Example class BNRDrawView: UIView, UIGestureRecognizerDelegate { private let moveRecognizer: UIPanGestureRecognizer }
50. Init Code Conversion Example @implementation BNRDrawView - (instancetype)initWithFrame:(CGRect)r { self = [super initWithFrame:r]; if (self) { self.moveRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(moveLine:)]; [self addGestureRecognizer:self.moveRecognizer]; } return self; }
51. Init Code Conversion Example override init(frame: CGRect) { moveRecognizer = UIPanGestureRecognizer(target: self, action: "moveLine:") addGestureRecognizer(moveRecognizer) super.init(frame: frame) }
52. Init Code Conversion Example override init(frame: CGRect) { moveRecognizer = UIPanGestureRecognizer(target: self, action: "moveLine:") addGestureRecognizer(moveRecognizer) super.init(frame: frame) } 'self' used before super.init call
53. Init Code Conversion Example override init(frame: CGRect) { super.init(frame: frame) moveRecognizer = UIPanGestureRecognizer(target: self, action: "moveLine:") addGestureRecognizer(moveRecognizer) } Property 'self.moveRecognizer' not initialized at super.init call
54. Init Code Conversion Example class BNRDrawView: UIView, UIGestureRecognizerDelegate { private let moveRecognizer: UIPanGestureRecognizer! }
55. Init Code Conversion Example override init(frame: CGRect) { super.init(frame: frame) moveRecognizer = UIPanGestureRecognizer(target: self, action: "moveLine:") addGestureRecognizer(moveRecognizer) } // No error
56. IBOutlets @property (nonatomic, weak) IBOutlet UIDatePicker *datePicker; ! @IBOutlet weak var datePicker: UIDatePicker? @IBOutlet weak var datePicker: UIDatePicker!
57. Custom Setters @property (nonatomic, strong) BNRItem *containedItem; // … - (void)setContainedItem:(BNRItem *)containedItem { _containedItem = containedItem; self.containedItem.container = self; }
58. Computed Properties var containedItem: BNRItem? { get { ! } set { } }
59. willSet/didSet var containedItem: BNRItem? { didSet { if let containedItem = containedItem { containedItem.container = self } } }
60. Privately Mutable Public Properties ! @interface BNRItemStore () @property (nonatomic, readonly) NSArray *allItems; @end ! @interface BNRItemStore () @property (nonatomic) NSMutableArray *privateItems; @end
61. Privately Mutable Public Properties ! ! class BNRItemStore { private(set) var allItems = [BNRItem]() }
62. More Information ! ! David Kobilnyk dkobilnyk@shoprunner.com github.com/davidkobilnyk/BNRGuideSolutionsInSwift !