Swift - Speaker Deck

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Swift Denis Lebedev, iOS @ Yandex

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Agenda • Introduction • Objective-C bridging • Good-to-know features • “Where can I Swift?”

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Swift Chris Lattner, Swift creator

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Swift • Multi-paradigm • Static, inferred typing • Bridged with Objective-C • No pointers

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–Someone at WWDC Keynote It’s like “Objective-C without C.”

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Swift features • Namespacing* • Generic classes & functions • Named/default parameters • Functions are ﬁrst class citizens • Optional types

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Optionals • Used in situations where value may be absent • Alternative for obj-c nil passing • works with any type

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Optionals - (NSInteger)indexOfObject:(id)object;

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Optionals func indexOf(object: AnyObject) -> Int?

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Optionals • Can be safely unwrapped (if/else) • Can be force unwrapped (runtime exception if value is missing)

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Classes, structs, enumerations • Classes passed by reference, structs - by value • Using a struct has no runtime penalty • All scalars and even Bool are structs • Enumerations are extremely powerful

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Enumerations enum Tree { case Empty case Leaf case Node }

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Enumerations enum Tree { case Empty case Leaf(Int) case Node(Tree, Tree) }

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Enumerations enum Tree { case Empty case Leaf(T) case Node(Tree, Tree) }

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Enumerations let tree: Tree = .Node(.Leaf(1), .Leaf(1))

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Enumerations enum Tree { case Empty case Leaf(T) case Node(Tree, Tree) ! func depth(t: Tree) -> Int { return 0 } }

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Enumerations enum Tree { case … ! func depth() -> Int { func _depth(t: Tree) -> Int { return 0 } return _depth(self) } }

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Enumerations enum Tree { case … ! func depth() -> Int { func _depth(t: Tree) -> Int { switch t { case .Empty: return 0 } return _depth(self) } }

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Enumerations enum Tree { case … ! func depth() -> Int { func _depth(t: Tree) -> Int { switch t { case .Empty: return 0 case .Leaf(let _): return 1 } return _depth(self) } ! }

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Enumerations enum Tree { case … ! func depth() -> Int { func _depth(t: Tree) -> Int { switch t { case .Empty: return 0 case .Leaf(let _): return 1 case .Node(let lhs, let rhs): return max(_depth(lhs), _depth(rhs)) } } return _depth(self) } }

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Enumerations enum Tree { case Empty case Leaf(T) case Node(Tree, Tree) ! func depth() -> Int { func _depth(t: Tree) -> Int { switch t { case .Empty: return 0 case .Leaf(let _): return 1 case .Node(let lhs, let rhs): return max(_depth(lhs), _depth(rhs)) } } return _depth(self) } }

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Collections • Array, Dictionary, String (contains Char) • Collections are structs • Implicitly bridged to Cocoa collection types

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Collections func filter(…) -> Bool) -> FilterSequenceView ! func reverse(source: C) -> ReverseView Some of operations are lazy evaluated

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Collections func filter(…) -> Bool) -> FilterSequenceView ! func reverse(source: C) -> ReverseView Some of operations are lazy evaluated

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Built-in immutability var b = 3 b += 1 ! let a = 3 a += 1 // error

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Dictionary immutability let d = ["key0": 0] ! d["key"] = 3 //error d.updateValue(1, forKey: "key1") //error

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Array immutability let c = [1, 2, 3] ! c[0] = 3 // success c.append(5) // fail

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Array immutability let c = [1, 2, 3] ! c[0] = 3 // success c.append(5) // fail It’s a bug: ! https://devforums.apple.com/message/971330#971330

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Extensions • extends any named type (struct, enum, class) • structures code

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Extensions struct Foo { let value : Int } ! extension Foo : Printable { var description : String { get {return "Foo"} } } ! extension Foo : Equatable { } ! func ==(lhs: Foo, rhs: Foo) -> Bool { return lhs.value == rhs.value }

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What Swift is missing • Preprocessor • Exceptions • Access control * • KVO, KVC • Compiler attributes (platforms, deprecations, etc.) • performSelector: is unavailable

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Objective-C bridging • Call Obj-c from Swift • Call Swift from Objc with limitations • Call CoreFoundation types directly • C++ is not allowed (should be wrapped in Objc) • Subclassing Swift classes not allowed in Objc

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Objective-C bridging • NSArray < - > Array • NSDictionary < - > Dictionary • NSNumber - > Int, Double, Float

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Objective-C bridging @objc class Foo { init (bar: String) { /*...*/ } }

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Objective-C bridging @objc(objc_Foo) class Foo { ! @objc(initWithBar:) init (bar: String) { /*...*/ } ! }

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Objective-C bridging Foo *foo = [[Foo alloc] initWithBar:@"Bar"];

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Objective-C bridging func convertPoint(point: CGPoint, toWindow window: UIWindow!) -> CGPoint - (CGPoint)convertPoint:(CGPoint)point toWindow: (UIWindow *)window

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Objective-C bridging • All object types are mapped as implicitly unwrapped optionals (T!) • All ‘id’ types are mapped as ‘AnyObject’

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Swift internals • Swift objects are Obj-c objects • Implicit root class ‘SwiftObject’ • Ivars type encoding is stored separately • Method’s vtable • Name mangling

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Name mangling class Foo { func bar() -> Bool { return false } } _TFC9test3Foo3barfS0_FT_Sb Swift keeps function metadata encoded in function symbols

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Performance • 10-100 x slower than C++ (-O0) • 10 x slower than C++ (-O3) • 1 x as C++ (-Ofast)*

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Performance • Swift is still in beta • Unoptimized calls of retain/release in loops

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Cross-platform code #if os(iOS) typealias View = UView #else typealias View = NSView #endif ! class MyControl : View { }

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Pattern matching let point = (0, 1) ! if point.0 >= 0 && point.0 <= 1 && point.1 >= 0 && point.1 <= 1 { println("I") } ! ...

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Pattern matching let point = (0, 1) ! switch point { case (0...1, 0...1): println("I") … }

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Pattern matching let point = (0, 1) ! switch point { case (0, 0): println("Point is at the origin") case (0...1, 0...1): println("I") case (-1...0, 0...1): println("II") case (-1...0, -1...0): println("III") case(0...1, -1...0): println("IV") default: println(“I don’t know.") }

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Function currying func add(a: Int)(b: Int) -> Int { return a + b } ! let foo = add(5)(b: 3) // 8 ! let add5 = add(5) // (Int) -> Int let bar = add5(b: 3) // 8

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Auto closures • Wraps function argument in explicit closure func assert(condition:() -> Bool, message: String) { #if DEBUG if !condition() { println(message) } #endif } ! assert({5 % 2 == 0}, "5 isn't an even number.")

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Auto closures Wraps function argument in explicit closure func assert(condition: @auto_closure () -> Bool, message: String) { #if DEBUG if !condition() { println(message) } #endif } ! assert(5 % 2 == 0, "5 isn't an even number.")

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Implicit type conversion struct Box { let _value : T init (_ value: T) { _value = value } } ! let boxedInt = Box(1) //Box

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Implicit type conversion func foo(i: Int) {…} ! foo(boxedInt) //error: ’Box' is not convertible to 'Int'

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Implicit type conversion extension Box { @conversion func __conversion() -> T { return _value } } ! ! foo(boxedInt) //success

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Implicit type conversion • allows any type to be ‘nil’ (which has NilType) • allows toll-free-bridging with Cocoa types

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Reﬂection struct Foo { var str = "Apple" let int = 13 func foo() { } } ! ! reflect(Foo()).count // 2 ! reflect(Foo())[0].0 // "str" reflect(Foo())[0].1.summary // "Apple

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Direct call of C functions @asmname - allows to provide a Swift interface for C functions @asmname("my_c_func") func my_c_func(UInt64, CMutablePointer) -> CInt;

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Scripting and REPL • xcrun swift - launches REPL • xcrun -i ‘ﬁle.swift’ - executes script

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Where can I swift? • BDD Testing framework: Quick! • Reactive programming: RXSwift • Model mapping: Crust • Handy JSON processing: SwiftyJSON

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Thx! @delebedev [email protected]

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Credits • http://nondot.org/sabre/ • https://devforums.apple.com/thread/227288 • http://andelf.github.io/blog/2014/06/08/swift-implicit-type-cast/ • https://www.youtube.com/watch?v=Ii-02vhsdVk • http://www.eswick.com/2014/06/inside-swift/ • http://article.gmane.org/gmane.comp.compilers.clang.devel/37217 • http://stackoverﬂow.com/questions/24101718/swift-performance-sorting-arrays • http://www.splasmata.com/?p=2798 • https://github.com/rodionovd/SWRoute/wiki/Function-hooking-in-Swift