swift rocks! #1
TRANSCRIPT
Swift Rocks!
Anton Mironov Software Engineer at 1
Everything started with
Low Level Virtual Machine
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Recent Objective-C features
• Blocks (closures)
• Automatic Reference Counting
• Literals
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Swift is a next next step
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Genius behind all of this
PhD Chris Lattner @clattner_llvm
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Swift is based on• Objective-C
• Haskel
• Ruby
• Python
• C#
• and many others
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First Lines of Code
print("Hello World!")
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First Lines of Code
print("\(name), I am your father")
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First Lines of Code
var name = "Luke" print("\(name), I am your father")
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First Lines of Code
var name = "Luke" let role = "father" print("\(name), I am your \(role)")
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Operators
let a = 3 let b = 4 let sum = a + b
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Operators
infix operator + { associativity left precedence 140 }
func +(lhs: Int, rhs: Int) -> Int
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No Autocasting
let a = 3 let b = 4.5 let sum = a + b
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No Autocasting
let a = 3 let b = 4.5 let sum = Double(a) + b
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Auto casting can be EvilNSEventModifierFlags modifierFlags = NSApp.currentEvent.modifierFlags;
BOOL isControlKeyPressed = modifierFlags & NSControlKeyMask;
if (isControlKeyPressed) { NSLog(@"Control pressed"); } else { NSLog(@"Control NOT pressed"); }
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Branching
if 0 == number % 2 { print("even") } else { print("odd") }
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Branching
let string = (0 == number % 2) ? "even" : "odd"
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Branchingswitch numberOfApples { case 0: return "none" case 6...10: return "just right" case 42, -1: return "let me see" case let value where (1 == value % 2): return "that's odd" default: return "this is unacceptable" } 18
Collections: Array
let arrayOfInts = [5, 4, 3, 2, 1]
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Collections: Set
let setOfInts: Set<Int> = [ 5, 4, 3, 2, 1 ]
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Collections: Dictionary
let dictionaryOfNamesByDigit = [ 5: "five", 4: "four", 3: "three", 2: "two", 1: "one" ]
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Cycles: Precondition
var i = 0 while i < 5 { print("value \(i)") i++ }
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Cycles: Postcondition
var i = 0 repeat { print("value \(i)") i++ } while i < 5
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Cycles: Counter
for var i = 0; i < 5; i++ { print("value \(i)") }
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Cycles: Enumeration
let arrayOfInts = [5, 4, 3, 2, 1] for value in arrayOfInts { print("\(value)") }
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Objective-C: Null Object Pattern
id operation = nil; [operation start];
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Swift: Optionals
let operation: NSOperation? = nil operation?.start()
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Swift: Optionals
if nil != person { return "Hello \(person!)" } else { return "Hello to nobody" }
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Swift: Optionals
if let nonNullPerson = person { return "Hello \(nonNullPerson)" } else { return "Hello to nobody" }
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Swift is Great for Imperative Programming
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Functionsfunc name(args) -> ReturnType { … }
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Functions: named arguments
func buildMessageForPerson( person: String, role: String) -> String { return "\(name), I am your \(role)" }
let message = buildMessageForPerson("Luke", role: "father" )
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Functions: default valuesfunc buildMessageForPerson( person: String = "Luke", role: String) -> String { return "\(person), I am your \(role)" }
let message = buildMessageForPerson( role: "father" )
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Functions: multiple returnfunc divide( a: Int, _ b: Int ) -> (result: Int, modulo: Int) { return (a / b, a % b) }
let result = divide(11, 4).result let modulo = divide(11, 4).modulo
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Functions are First Class Citizen
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Functions as arguments Simple Example
func add(a: Int, b: Int) -> Int { return a + b } func mul(a: Int, b: Int) -> Int { return a * b }
func runMathOp(a: Int, _ b: Int, op: (Int, Int) -> Int ) -> Int { return op(a, b) }
let value1 = runMathOp(4, 3, op: add) let value2 = runMathOp(4, 3, op: mul)
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Functions as arguments Simple Example
func runMathOp(a: Int, _ b: Int, op: (Int, Int) -> Int ) -> Int { return op(a, b) }
let value1 = runMathOp(4, 3, op: +) let value2 = runMathOp(4, 3, op: -)
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Swift is Functional Language
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Imperative Stylelet names = ["Luke", "Chuwy", "Baker"] var messages = [String]()
for name in names { let message = buildMessageForPerson(name, "father") messages.append(message) }
print("\(messages)")
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Functional Stylelet names = ["Luke", "Chuwy", "Baker"] let messages = names.map { buildMessageForPerson($0, "father") }
print("\(messages)")
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Closuresfunc buildOperation(multiplier: Int ) -> (Int -> Int) { func multiply(value: Int) -> Int { return value * multiplier }
return multiply }
let operation = buildOperation(3) let value = operation(4)
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Just use Functional Paradigm
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Type System
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Type System Classification Criteria: Parameters Passing and Ownership• By Value let a = 3
• By Sharing (by reference to shared object) let userDefaults = NSUserDefaults.standardUserDefaults()
• By Reference let operation = myFunction let c = operation(a, b)
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Type System Classification Criteria: OOP
• Encapsulation
• Inheritance
• Polymorphism
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Type System Classification Criteria: Access Control
• Public - visible for importers
• Internal (default) - visible within module
• Private - visible within file
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Type System Classification Criteria: Objective-C compatibility• partial
• none
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Types• tuple
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Types• tuple
• function
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Classesclass Transport {
} 50
Classesclass Transport { let name: String
} 51
Classesclass Transport { let name: String private var velocity: Double = 0.0
} 52
Classesclass Transport { let name: String private var velocity: Double = 0.0 init(name: String) { self.name = name }
} 53
Classesclass Transport { let name: String private var velocity: Double = 0.0 init(name: String) { self.name = name } func beep() { print("Beep!") } } 54
Classeslet transport = Transport( name: "kinda boat" )
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Classeslet transport = Transport( name: "kinda boat" ) transport.beep()
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Classeslet transport = Transport( name: "kinda boat" ) transport.beep() transport.speed = 10.0
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Classesclass Car: Transport { var color: String = "Red" }
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Classesclass Car: Transport, Paintable, Movable { var color: String = "Red"
… }
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Classes Strong Referenceclass Person { var transport: Transport }
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Classes Weak Referenceclass Car: Transport { weak var passanger: Passanger? }
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Classes Unowned Reference
class Node { unowned var parentNode: Node }
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Structuresstruct Point2D { var x: Double var y: Double
init(x: Double, y: Double) { self.x = x self.y = y } }
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Structuresvar point1 = Point2D(x: 1.0, y: 2.0) var point2 = point1 point1.x = 3.0
// (point1.x != point2.x)
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Structureslet point1 = Point2D(x: 1.0, y: 2.0) // point1 is immutable
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Structuresstruct Point2D { var x: Double var y: Double … mutating func multiply(
mult: Double) { self.x *= mult self.y *= mult } }
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Structures are everywhere• Int, Bool, UInt64, Float, Double, …
• String
• Array, Set, Dictionary
• …
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Enumsenum TokenStatus: String { case None = "none" case Valid = "valid" case Invalid = "invalid" case Expired = "expired"
var shouldRefetch: Bool { return .Valid == self } }
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Enums (Unions)enum FileSystemError: ErrorType { case InvalidURL(NSURL) case InvalidPermissions case UnknownErrorCode(Int) }
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Enums (Unions)switch fileSystemError { case .InvalidURL(let URL): print("Invalid URL \(URL)") case .InvalidPermissions: print("Invalid permissions") case .UnknownErrorCode(let code) where code == -150: print("I've seen this error somewhere") case .UnknownErrorCode(let code): print("Something gone very wrong \(code)") }
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Protocolsprotocol Drawable { var boundingRect: NSRect { get } func draw() }
struct Polygon: Drawable { var points = [NSPoint]() //MARK: Drawable var boundingRect: NSRect? { ... } func draw() { ... } } 71
Generic Functionsfunc min<T: Comparable>( lhs: T, _ rhs: T ) -> T { return lhs < rhs ? lhs : rhs }
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Generic Typesstruct Point<T: FloatingPointType> { var x: T var y: T }
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Extensionsextension NSDate { var myBirthday: NSDate { … } }
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Protocols + Extensions + Generics = ❤
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Swift
Objective-C
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Simple or Complex?
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Swift on Prod
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Just use It!
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