Swift

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Examples

Classes

class MyClass : OptionalSuperClass, OptionalProtocol {
    var myProperty: String

    // Initializer (initialize all non-optionals)
    init(myProperty: String) {
        // use self.varName if argument has the same name
        self.myProperty = myProperty
    }
}

Methods

class MyClass {
    func doIt() -> Int {
        return 0
    }
    func doIt(a: Int) -> Int {
        return a
    }
    func doIt(a: Int, b: Int) -> Int {
        return a + b
    }
}
var instance = MyClass()
let variable1 = instance.doIt()
let variable2 = instance.doIt(1)
let variable3 = instance.doIt(1, b: 2)

Properties

// Properties
var myProperty: String
var myOptionalProperty: String?

// Public Property with Private Setter
// (e.g. for objects with public properties that can only be set internally)
public private(set) var myOtherProperty: String
public private(set) var myOtherOptionalProperty: String?

// Computed Properties
var myInt: Int = 1
var doubleInt: Int {
    get { return myInt * 2 }
    set { myInt = newValue / 2 }
}

// Read-Only Computed Properties
var tripleInt: Int {
    return myInt * 3
}

// Property Observers
var myOutput = 0 {
    willSet {
        print("setting myOutput to \(newValue)")
    }
    didSet { // never set greater than 10
        if myOutput > 10 {
            myOutput = 10
        }
    }
}

Subscripts

struct HTMLElement {
    var id = "hello"
    var style = "color: red;"

    // Can have any number of parameters
    // Can return any type
    subscript(attr: String) -> String {
        get {
            if attr == "id"    { return id    }
            if attr == "style" { return style }
            return ""
        }

        set {
            // "newValue" contains the... new value
            if attr == "id"    { id    = newValue }
            if attr == "style" { style = newValue }
        }

    }
}

let el = HTMLElement()
print(el["id"])     // prints "hello"
el["style"] = "float: left;"
print(el["style"])  // prints "float: left;"

Objects

let a = MyClass(myProperty: "Hello")
a.myProperty = "World"
a.myFunc()

Extensions

extension Double {
    var isNegative: Bool { return isSignMinus }
}
let myDouble = -2.0
myDouble.isNegative
// returns true

Closures

func myclosure(number: Int) -> Int {
  return number + 1
}
numbers.map(myclosure)
// returns [2, 3, 4, 5]

let animals = ["fish", "cat", "elephant", "dog", "minion"]
let sortedAnimals = animals.sorted { (first, second) in first > second }
sortedAnimals = animals.sorted { $0 > $1 } // $0 and $1 mean first and second params respectively

let evenCheckFunction = isEven
let odds = Array(1...10).filter(!isEven)
odds = Array(1...10).filter { (number) in number % 2 != 0 }
odds = Array(1...10).filter { $0 % 2 == 0 }

Protocols

protocol MyProtocol {
    var myProperty: String? { get set }
    func myMethod()
}
class MyClass : MyProtocol {
    // Protocol implementation
    // Variables
    var myProperty: String?
    // Methods with body
    func myMethod() {
        print("Hello from protocol")
    }
}

Enums

enum CompassPoint {
    case North, South, East, West
}
var direction = CompassPoint.North
// As direction is a CompassPoint, short syntax is usable
direction = .South

// Raw Values
enum CollisionType: Int {
    case Player = 1
    case Enemy = 2
}
let type = CollisionType.Player
if type == .Player {
    print("It's a Player")
}
type.rawValue == 2 // false

// Associated Values
enum Computer {
    case Desktop(Int, String)
    case Laptop(Int, String)
}
var something = Computer.Laptop(8, "i7")
switch something {
case .Laptop(let ram, let cpu):
    print("It's a \(cpu) Laptop with \(ram) GB ram.")
default:
    print("What else can it be?")
}

// Check enum value with switch
switch direction {
case .North:
    print("The direction is North")
case .East:
    print("The direction is East")
case .South:
    print("The direction is South")
case .West:
    print("The direction is West")
// Either check for all cases or implement the default: case
}

Variables

var mutableDouble: Double = 1.0
mutableDouble = 2.0
let constantDouble: Double = 1.0
// constantDouble = 2.0 // will generate an error

var mutableInferredDouble = 1.0
var optionalDouble: Double? = nil
optionalDouble = 1.0

if let definiteDouble = optionalDouble {
    definiteDouble
}

Optionals

var s: String?
s = "needle"
s = nil

let forced: String = s! // error if nil

if let forced = s {
  print(forced)
} else {
  print("not found")
}

let forced:String = s ?? "default value" //if (s == nil) use default value

Control Flow

var condition = true
if condition {
    // do something
} else {
    // do something else
}

guard condition else {
    // return or throw
}

defer {
    // execute when leaving scope
    // regardless of how scope is left
    print("Cleaning Up!")
}

var val = 5
switch val {
case 1:
    "foo"
case 2:
    "bar"
default:
    "baz"
}

let point = (1,1)
switch point {
  case (let x, 0): print("point on x with displacement of \(x)")
  case (0, _): print("point on y")
  case (1...5, 1...5): print("point within bounds")
  case let (x,y) where x == y: print("point is on line")
  case let (x,y): print("point out of bounds at \(x), \(y)")
}

// omits upper value, use ... to include
for i in 0..<3 {
}
// when no index is needed
for _ in 0..<3 {
}

// Labeled Statements
let matrix = [[1,2,3],[4,5,6],[7,8,9]]
TheLoop: for column in matrix {
    for item in column {
        if item == 5 {
            break TheLoop
        }
    }
}

Error Handling

// ErrorType
enum MyError : ErrorType {
    case Err1
    case Err2(errDesc: String)
}

// Throwing
func throwingFunc() throws -> Int {
    // You can propogate throw to calling function
    try otherThrowingFunc()

    // You can directly throw error
    guard safeCondition == true else {
        throw MyError.Err1
    }
}

// do, try, catch
do {
    // Perform any throwable operation in here
    try throwingFunc()
} catch MyError.Err2(let desc) {
    // Catches have same pattern matching capability as Enum cases
    print(desc)
} catch {
    // Catch anything that the above catches didn't catch
    print("Some Error")
}

// try!, try?

// Causes a runtime error when error is thrown
let result = try! throwingFunc()

// Returns the result of throwingFunc as an optional; nil on throw
let result: Int? = try? throwingFunc()

Strings

let personOne = "Ray"
let personTwo = "Brian"
let combinedString = "\(personOne): Hello, \(personTwo)!"
var tipString = "2499"
let tipInt = tipString.toInt()

extension Double {
    init (string: String) {
        self = (string as NSString).doubleValue
    }
}
tipString = "24.99"
let tip = Double(string: tipString)

Arrays

let person1 = "Ray"
let person2 = "Brian"
var array: [String] = [person1, person2]
array += ["Waldo"]
for person in array {
    print("person: \(person)")
}
let waldo = array[2]

Dictionaries

var dict: Dictionary<String, String> = ["Frog": "Kermit", "Pig": "Ms. Piggy", "Weirdo": "Gonzo"]
dict["Weirdo"] = "Felipe"
dict["Frog"] = nil // delete frog
for (type, muppet) in dict {
    print("type: \(type), muppet: \(muppet)")
}

Tuples

let p1 = (1,2)
let p2 = (x:1, y:2)

let (x1,y1) = p1
let (x1,_) = p1
let x1 = p1.0, y1 = p1.1

let x = p2.x, y = p2.y