Swift, meet Objective-C

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! Swift, meet Objective-C ! Twitter: @DanToml Email: [email protected]

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In the sharp, square bracketed embrace of Objective-C — @AndrewJClark

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All objective-c written now is technical debt

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...but so is all of your Swift.

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You can use them together

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A whole bunch of new developers are going to be Swift only.

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Starting out

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Starting out Bridging Header // // Use this file to import your target's public headers that you would like to expose to Swift. // #import "Person.h" #import "PersonController.h" #import "CoreDataController.h"

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Objective-C -> Swift

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The bridging header // ReactiveCocoa-Bridging-Header.h // // Use this file to import your target's public headers that you would like to expose to Swift. // #import "RACCommand.h" #import "RACDisposable.h" #import "RACEvent.h" #import "RACScheduler.h" #import "RACTargetQueueScheduler.h" #import "RACSignal.h" #import "RACSignal+Operations.h" #import "RACStream.h" #import "RACSubscriber.h"

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Method Names // Objective-C - (instancetype)initWithArray:(NSArray *)array title:(NSString *)title; // Swift init!(array: [AnyObject]!, title: String!)

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Method Names // Objective-C - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions; // Swift func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool

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Nullability • __nullable • __nonnull • __null_resettable // Properties only. • null_unspecified // Default.

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Nullability Before // Objective-C @interface XYZList : NSObject - (XYZListItem *)itemWithName:(NSString *)name; @property (copy, readonly) NSArray *allItems; @end // Swift class XYZList : NSObject, NSCoding, NSCopying { func itemWithName(name: String!) -> XYZListItem! @NSCopying var allItems: [AnyObject]! { get } }

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Nullability After // Objective-C @interface XYZList : NSObject - (XYZListItem * __nullable)itemWithName:(NSString * __nonnull)name; @property (copy, readonly) NSArray * __nonnull allItems; @end // Swift class XYZList : NSObject, NSCoding, NSCopying { func itemWithName(name: String) -> AAPLListItem? @NSCopying var allItems: [AnyObject] { get } }

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Swift -> Objective-C

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What can be bridged? • Classes

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Classes // Swift @objc class MySwiftNSObject { var array: [String] init(array: [String]) { self.array = array; } } // Objective-C @interface MySwiftNSObject @property (nonatomic, copy) NSArray * __nonnull array; - (instancetype)initWithArray:(NSArray * __nonnull)array OBJC_DESIGNATED_INITIALIZER; @end

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What can be bridged? • Classes • Protocols

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Protocols @objc protocol Edible { func eat() } @protocol Edible { - (void)eat; }

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What can be bridged? • Classes • Protocols • Methods

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Methods func genericFunction(param: T) // Not bridged func defaultParameterFunction(param: String = "Hi") // Not bridged func function(param: String) - (void)function:(NSString * __nonnull)param;

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What can be bridged? • Classes • Protocols • Methods • Properties

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Properties // Swift let forname: String var surname: String // Objective-C @property (nonatomic, readonly, copy) NSString * __nonnull forname; @property (nonatomic, copy) NSString * __nonnull surname;

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Properties KVO (Key Value Observing) dynamic var name: String object.addObserver(self, forKeyPath: "name", options: .New, context: &myContext)

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What can be bridged? • Classes • Protocols • Methods • Properties • Enums

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Enums @objc enum MyEnum : Int { case SomeValue = 0 case AnotherValue = 1 } typedef NS_ENUM(NSInteger, MyEnum) { MyEnumSomeValue = 0, MyEnumAnotherValue = 1 };

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Bridging limitations !!! No: - Structs - Functions - Operators - Generics - Subclassing Swift classes in objective-c

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Roundup

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Further Resources Apple • WWDC Session 406 (Integrating Swift with Objective-C) • WWDC Session 407 (Swift Interoperability in Depth) Blog Posts • https://mikeash.com/pyblog/friday-qa-2014-08-15-swift- name-mangling.html

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Questions? Twitter: @DanToml Email: [email protected]