Porting Objective-C to Swift. Richard Ekle

Transcription

1 Porting Objective-C to Swift Richard Ekle

2 Why do we need this? 1.2 million apps in the ios App Store All written in Objective-C Will need porting to Swift in the future. Possible Swift-only APIs in the future.

3 Calling object methods Objective-C [self presentviewcontroller:controller animated:yes completion:nil]; Swift self.presentviewcontroller(controller, animated:true, completion:nil)

4 Declaring Classes

5 Objective-C vs Swift Classes Objective-C Header file: ClassName.h Implementation file: ClassName.m Swift No header file Implementation file: ClassName.swift (class)

6 Objective-C Class Header File: ClassName { // Member variable int avalue; } // (strong) UILabel *alabel; // Instance method - (bool) islabelvisible; // Class method + (UILabel*)

7 Objective-C Class Implementation File: ClassName.m #import ClassName - (bool) islabelvisible { ++avalue; return!self.alabel.hidden; } + (UILabel*) newlabelwithtitle:(nsstring*)title { UILabel *newlabel = [[UILabel alloc] init]; newlabel.text = title; return newlabel

8 Swift Class File: ClassName.swift class ClassName { // Property (optional) var alabel: UILabel? // Instance method func islabelvisible -> bool { return!self.alabel.hidden } // Class method class func newlabelwithtitle(title: string) -> UILabel { var newlabel = UILabel() newlabel.text = title return newlabel } }

9 Objective-C Initializers ClassName - (id) init { // } - (id) initwithtitle:(nsstring*)title { //

10 Swift Initializers (constructor) class ClassName { init() { // } init(title:string) { // } }

11 Objective-C Deinitializers ClassName - (void) dealloc { //

12 Swift Deinitializers (destructor) class ClassName { deinit { // } }

13 Object Allocation Objective -C ClassName *aclass = [[ClassName alloc] init]; ClassName *aclass2 = [[ClassName alloc] initwithtitle:@ Title ]; Swift var aclass = ClassName() var aclass2 = ClassName(title: title )

14 Objective-C Properties

15 Objective-C Property Getter/Setter methods (nonatomic, strong) UILabel* Getter / // Getter - (UILabel*) labelview { return _labelview; } // Setter - (void) setlabelview:(uilabel*)aview { _labelview = aview;

16 Calling Objective-C property getter/setter methods Getter UILabel *label = [aclass labelview]; UILabel *label = aclass.labelview; Setter [aclass setlabelview:label]; aclass.labelview = label;

17 synthesize / dynamic synthesize - Tells compiler to auto-generate getter/ setter methods of an Objective-C labelname; dynamic - Tells compiler that YOU will write the getter/ setter methods of an Objective-C labelname; Both optional now. Compiler will generate properties automatically.

18 Swift Properties

19 Swift Properties class ClassName { // Stored property var avalue: int // Computed property var count: int { get { return avalue; } set(newcount) { avalue = newcount; } } }

20 Objective-C enum AlertViewType { Unknown, Ok, Cancel } Swift enum AlertViewType { case Unknown case Ok case Cancel } Enumerations

21 Objective-C Switch statements switch (aval) { } case 1: case 2: // do something break; case 3: // do something break;

22 Must be exhaustive Swift Switch statements Do not normally fall through to the next case. Add fallthrough keyword to enable fall through No break needed on each case. switch aval { case 1: fallthrough case 2: // do something case 3: // do something default: // do something }

23 Strings Objective-C NSString *x This is a test ; Swift var x = This is a test Just remove symbol before the string

24 Mutable / Immutable objects Objective-C NSMutableArray / NSArray NSMutableDictionary / NSDictionary NSMutableString / NSString Swift // Mutable var name = John Smith var info = [ FirstName : John, LastName : Smith ] var petnames = [ Spot, Fido, Cerebrus ] // Immutable let name2 = John Smith let info2 = [ FirstName : John, LastName : Smith ] let petnames = [ Spot, Fido, Cerebrus ]

25 Calling Objective-C from Swift

26 Objective-C bridging header Filename: <TargetName>-Bridging-Header.h Auto-created by Xcode the first time you add a Swift class to a project Make sure you add this file to your project / source control! Any classes defined in this header are automatically visible to Swift code Manually add #include/#import lines to this file to include any Objective-C classes you want visible from Swift Allocate/call Objective-C classes from Swift as if they were standard Swift classes

27 Calling Swift from Objective-C

28 Marking Swift classes visible to Objective-C attribute to Swift class ClassName { // Definition of class }

29 Swift Module Header Include in Objective-C code to include Swift classes callable from Objective-C Auto generated by Xcode. File name: <ModuleName>-Swift.h

30 Using Swift classes in Objective-C code Include Swift module header #import ModuleName-Swift.h Allocate and call as if it is a regular Objective-C class ClassName *aclass = [[ClassName alloc] init]; [aclass somemethod:param1 width:10 height:20];

31 Resources Apple WWDC ios App WWDC 2014 Videos Session 402: Introduction to Swift Session 403: Intermediate Swift Session 404: Advanced Swift Session 406: Integrating Swift with Objective-C