An introduction to Swift. Sasha

Transcription

1 An introduction to Swift Sasha

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3 Exhibit A + (NSUInteger)indexOfString:(NSString *)str inarray:(nsarray *)arr { return [arr indexofobject:str]; // 1) if 'str' is nil, we return NSNotFound // 2) if 'arr' is nil, we return 0

4 Exhibit B NSMutableArray *array = [NSArray array]; [array addobject:@"hello"]; // This compiles and crashes at runtime with: // "-[ NSArrayI addobject:]: unrecognized selector // sent to instance 0x7a3141c0"

5 Exhibit C NSMutableArray *array = [NSMutableArray array]; [array addobject:@"hello"]; [array addobject:@17]; // This compiles just fine NSString *string = array[1]; // This works and prints 17 NSLog(@"%@", string); // But this crashes NSLog(@"%@", [string stringbyappendingstring:@"hmm"]);

6 Enter: Swift Brand new, clean, modern Type safe, generic, functional Compiles to native (no JIT, no GC) Seamless interop with Objective-C Use all existing ios/os X APIs

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8 Key Language Principles Variables vs. constants Optional types Pattern matching First-class functions Full interop with Objective-C

9 Fresh OComplex : (nonatomic) double (nonatomic) double imag; - (instancetype)initwithreal:(double)real imag:(double)imag; - (double)magsquare; - (OComplex *)addto:(ocomplex *)other; - (OComplex *)multby:(ocomplex struct Complex { var real: Double, imag: Double func magsquare() -> Double {... func add(z: Complex) -> Complex {... func mult(z: Complex) -> Complex {... func +(z1: Complex, z2: Complex) -> Complex { return z1.add(z2) func *(z1: Complex, z2: Complex) -> Complex { return z1.mult(z2)

10 Fresh Air for (int x = 0; x < steps; ++x) { for (int y = 0; y < steps; ++y) { OComplex *z = [[OComplex alloc] initwithreal:0.0 imag:0.0]; int iters = 0; OComplex *c = [[OComplex alloc] initwithreal:xmin+xstep*x imag:ymin+ystep*y]; while ([z magsquare] < thresh && iters < conv) { z = [[z multby:z] addto:c]; ++iters; for x in 0..<steps { for y in 0..<steps { var z = Complex(real: 0, imag: 0) var iters = 0 let c = Complex(real: xmin+xstep*double(x), imag: ymin+ystep*double(y)) while z.magsquare() < thresh && iters < conv { z = z*z + c ++iters

11 Exhibit D let fareclass =... var milesbonus: Double switch fareclass { case "F", "A", "J", "C": milesbonus = 2.5 // business/first case "Y", "B": milesbonus = 2.0 // full-fare economy case "M", "H": milesbonus = 1.5 // top-tier discount economy case let fc where fc.hasprefix("r"): milesbonus = 0 // upgrades default: milesbonus = 1.0

12 Exhibit E enum HttpResponse { case Success(body: String) case Error(description: String, statuscode: Int) switch httpgetrequest(" { case let.error(desc, status) where status >= 500: println("internal server error: \(desc)") case let.error(desc, status): println("error \(status), msg = \(desc)") case.success(let body): println("success, body = \(body)")

13 Exhibit F extension Int { func repeat(task: Int -> ()) { for x in 0..<self { task(x) 3.repeat { println($0)

14 Exhibit G

15 Photo source: Wikipedia I call it my billion-dollar mistake. It was the invention of the null reference in [ ] I couldn't resist the temptation to put in a null reference, simply because it was so easy to implement. This has led to innumerable errors, vulnerabilities, and system crashes, which have probably caused a billion dollars of pain and damage in the last forty years. Sir Charles Antony Richard Hoare, 2009

16 Exhibit H let cell : AnyObject? = tableview. dequeuereusablecellwithidentifier("taskcell") if let cell = cell as? UITableViewCell { cell.textlabel?.text = task.text cell.detailtextlabel?.text = task.duedatestring return cell

17 Let s Build an App!

18 Interop with Objective-C Source: Using Swift with Cocoa and Objective-C, Apple

19 Swift 2.0 Error handling with try, throw, catch and defer blocks Protocol extensions Better interop with Objective-C (nullability annotations and generics)

20 Swift 3.0 Fully open source (on GitHub) Linux port Swift libraries layer, written in Swift

21 Thank You! Sasha