Swift is a new programming language that is statically typed, multi-paradigm, and designed to work with Cocoa and Cocoa Touch. It features modern language elements like optionals, generics, closures, and pattern matching. Swift code is compiled to native executables making it performant, and it is designed to bridge seamlessly with Objective-C and Cocoa allowing existing iOS and OS X apps to migrate code over.

1. Swift
Denis Lebedev, iOS @ Yandex

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

3. Swift
Chris Lattner, Swift creator

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

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

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

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

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

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

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

12. 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

13. Enumerations
enum Tree {
case Empty
case Leaf
case Node
}

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

15. Enumerations
enum Tree<T> {
case Empty
case Leaf(T)
case Node(Tree, Tree)
}

16. Enumerations
let tree: Tree<Int> = .Node(.Leaf(1), .Leaf(1))

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

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

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

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

21. Enumerations
enum Tree<T> {
case …
func depth() -> Int {
func _depth<T>(t: Tree<T>) -> 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)
}
}

22. Enumerations
enum Tree<T> {
case Empty
case Leaf(T)
case Node(Tree, Tree)
func depth() -> Int {
func _depth<T>(t: Tree<T>) -> 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)
}
}

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

24. Collections
func filter<S : Sequence>(…) -> Bool) ->
FilterSequenceView<S>
func reverse<C : Collection …>(source: C) ->
ReverseView<C>
Some of operations are lazy evaluated

25. Collections
func filter<S : Sequence>(…) -> Bool) ->
FilterSequenceView<S>
func reverse<C : Collection …>(source: C) ->
ReverseView<C>
Some of operations are lazy evaluated

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

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

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

29. 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

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

31. 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
}

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

33. 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

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

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

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

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

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

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

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

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

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

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

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

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

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

47. 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.")
}

48. 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

49. 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.")

50. 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.")

51. Implicit type conversion
struct Box<T> {
let _value : T
init (_ value: T) {
_value = value
}
}
let boxedInt = Box(1) //Box<Int>

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

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

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

55. 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

56. 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<UInt64>) -> CInt;

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

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

59. Thx!
@delebedev
lebedzeu@yandex-team.ru

60. 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