Swift 语言
      2014年6月3日发布，替代OBJECT-C
      Swift is a new programming language for creating iOS and OS X apps. Swift builds on the best of C and Objective-C, without the constraints of C compatibility. Swift adopts safe programming patterns and adds modern features to make programming easier, more flexible, and more fun. Swift’s clean slate, backed by the mature and much-loved Cocoa and Cocoa Touch frameworks, is an opportunity to reimagine how software development works.

文档
      https://itunes.apple.com/us/book/the-swift-programming-language/id881256329?mt=11
      http://download.csdn.net/detail/surfsky/7440835


helloWorld
    println("Hello, world")


-------------------------------------------------------------
基础
-------------------------------------------------------------
注释
    //
    /**/

分号
    单行无需加分号
    多个语句放在一行，需要加分号


变量
    var myVariable = 42

常量
    let myConstant = 42
    let explicitDouble: Double = 70


-------------------------------------------------------------
数据类型
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数字类型
    类型
          Int: Int32, Int64
          UInt: UInt32, Uint64
          Double
          Float
    各种表示方法
      let decimalInteger = 17
      let binaryInteger = 0b10001 // 17 in binary notation
      let octalInteger = 0o21 // 17 in octal notation
      let hexadecimalInteger = 0x11 // 17 in hexadecimal notation
      let decimalDouble = 12.1875
      let exponentDouble = 1.21875e1
      let hexadecimalDouble = 0xC.3p0
      let paddedDouble = 000123.456
      let oneMillion = 1_000_000

布尔（boolean）
    let orangesAreOrange = true
    let turnipsAreDelicious = false

向量
    let (statusCode, statusMessage) = (404, "Not Found")
    let (x, y) = (1, 2)
    let http200Status = (statusCode: 200, description: "OK")
    println("The status code is \(http200Status.statusCode)")

字符串
    let label = "The width is "
    let width = 94
    let widthLabel = label + String(width)
    字符串相加
        let apples = 3
        let oranges = 5
        let appleSummary = "I have \(apples) apples."
        let fruitSummary = "I have \(apples + oranges) pieces of fruit."
数组
    var shoppingList = ["catfish", "water", "tulips", "blue paint"]
    shoppingList[1] = "bottle of water"
    var occupations = ["Malcolm": "Captain", "Kaylee": "Mechanic",]
    occupations["Jayne"] = "Public Relations"
    let emptyArray = String[]()
    shoppingList = []

字典
    let emptyDictionary = Dictionary<String, Float>()
    emptyDictionary = [:]


空（nil）和可为空对象
    var serverResponseCode: Int? = 404
    serverResponseCode = nil
    ----------------------------------------------    
    let possibleString: String? = "An optional string."
    println(possibleString!)
    let assumedString: String! = "An implicitly unwrapped optional string."
    println(assumedString)

    

    
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数据流
-------------------------------------------------------------
if
    if i == 1 {
        // this example will compile successfully
    }


switch
    let vegetable = "red pepper"
    switch vegetable 
    {
        case "celery":
            let vegetableComment = "Add some raisins and make ants on a log."
        case "cucumber", "watercress":
            let vegetableComment = "That would make a good tea sandwich."
        case let x where x.hasSuffix("pepper"):
            let vegetableComment = "Is it a spicy \(x)?"
        default:
            let vegetableComment = "Everything tastes good in soup."
    }


for
    var firstForLoop = 0
    for var i = 0; i < 3; ++i {
        firstForLoop += 1
    }
    for i in 0..3 {
        firstForLoop += i
    }


for(遍历数组)
    let individualScores = [75, 43, 103, 87, 12]
    var teamScore = 0
    for score in individualScores {
        if score > 50 {
            teamScore += 3
        } else {
            teamScore += 1
        }
    }
    
for(遍历字典)
    let interestingNumbers = [
        "Prime": [2, 3, 5, 7, 11, 13],
        "Fibonacci": [1, 1, 2, 3, 5, 8],
        "Square": [1, 4, 9, 16, 25],
    ]
    var largest = 0
    for (kind, numbers) in interestingNumbers {
        for number in numbers {
            if number > largest {
                largest = number
            }
        }
    }



while
    var n = 2
    while n < 100 {
        n = n * 2
    }

do...while
    var m = 2
    do {
        m = m * 2
    } while m < 100
    
    
断言（assert）
    let age = -3
    assert(age >= 0, "A person's age cannot be less than zero")

    
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函数
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函数定义和调用
    func greet(name: String, day: String) -> String {
        return "Hello \(name), today is \(day)."
    }
    greet("Bob", "Tuesday")


返回多个数据
    func getGasPrices() -> (Double, Double, Double) {
        return (3.59, 3.69, 3.79)
    }
    getGasPrices()

不限个数参数
    func sumOf(numbers: Int...) -> Int {
        var sum = 0
        for number in numbers {
            sum += number
        }
        return sum
    }
    sumOf()
    sumOf(42, 597, 12)


嵌套函数
    func returnFifteen() -> Int {
        var y = 10
        func add() {
            y += 5
        }
        add()
        return y
    }
    returnFifteen()


返回函数变量
    func makeIncrementer() -> (Int -> Int) {
        func addOne(number: Int) -> Int {
            return 1 + number
        }
        return addOne
    }
    var increment = makeIncrementer()
    increment(7)

函数作为输入参数（类似lambda表达式）
    func hasAnyMatches(list: Int[], condition: Int -> Bool) -> Bool {
        for item in list {
            if condition(item) {
                return true
            }
        }
        return false
    }
    func lessThanTen(number: Int) -> Bool {
        return number < 10
    }
    var numbers = [20, 19, 7, 12]
    hasAnyMatches(numbers, lessThanTen)

闭包
    numbers.map({
        (number: Int) -> Int in
        let result = 3 * number
        return result
    })

用编号替代名字
    sort([1, 5, 3, 12, 2]) { $0 > $1 }


-------------------------------------------------------------
对象和类
-------------------------------------------------------------
类定义
    class Shape {
        var numberOfSides: Int = 0
        var name: String
        init(name: String) {
            self.name = name
        }
        func simpleDescription() -> String {
            return "A shape with \(numberOfSides) sides."
        }
    }

使用
    var shape = Shape()
    shape.numberOfSides = 7
    var shapeDescription = shape.simpleDescription()


self/super
    self  -> this
    super -> parent
    

继承
    class Square: NamedShape {
        var sideLength: Double
        init(sideLength: Double, name: String) {
            self.sideLength = sideLength
            super.init(name: name)
            numberOfSides = 4
        }
        func area() -> Double {
            return sideLength * sideLength
        }
        override func simpleDescription() -> String {
            return "A square with sides of length \(sideLength)."
        }
    }
    let test = Square(sideLength: 5.2, name: "my test square")
    test.area()
    test.simpleDescription()

属性
    var perimeter: Double {
        get {return 3.0 * sideLength}
        set {sideLength = newValue / 3.0}
    }


方法重载
    override func simpleDescription() -> String {
        return "An equilateral triagle with sides of length \(sideLength)."
    }

willSet和didSet（属性的值设置前后处理）
    var triangle: EquilateralTriangle {
        willSet {
            square.sideLength = newValue.sideLength
        }
    }

可为空对象方法调用
    let optionalSquare: Square? = Square(sideLength: 2.5, name: "optional square")
    let sideLength = optionalSquare?.sideLength

泛型

struct Pair<T: Equatable> {
    let a: T!
    let b: T!
    init(a: T, b: T) {
        self.a = a
        self.b = b
    }
    func equal() -> Bool {
        return a == b
    }
}

let pair = Pair(a: 5, b: 10)
pair.a // 5
pair.b // 10
pair.equal() // false
 

let floatPair = Pair(a: 3.14159, b: 2.0)
floatPair.a // 3.14159
floatPair.b // 2.0
floatPair.equal() // false

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枚举和结构体
-------------------------------------------------------------
枚举
    enum Rank: Int {
        case Ace = 1
        case Two, Three, Four, Five, Six, Seven, Eight, Nine, Ten
        case Jack, Queen, King
    
        func simpleDescription() -> String {
            switch self {
                case .Ace:                   
                     return "ace"               
                case .Jack:                
                     return "jack"                
                case .Queen:                 
                     return "queen"               
                case .King:                  
                     return "king"                
                default:                     
                     return String(self.toRaw())  
            }
        }
    }
    let ace = Rank.Ace           
    let aceRawValue = ace.toRaw()
    if let convertedRank = Rank.fromRaw(3) {
        let threeDescription = convertedRank.simpleDescription()
    }


看得有点晕
    enum ServerResponse {
        case Result(String, String)
        case Error(String)
    }
    let success = ServerResponse.Result("6:00 am", "8:09 pm")
    let failure = ServerResponse.Error("Out of cheese.")
    
    switch success {
        case let .Result(sunrise, sunset):
        let serverResponse = "Sunrise is at \(sunrise) and sunset is at \(sunset)."
        case let .Error(error):
    }


结构体
    struct Card {
        var rank: Rank
        var suit: Suit
        func simpleDescription() -> String {
            return "The \(rank.simpleDescription()) of \(suit.simpleDescription())"
        }
    }
    let threeOfSpades = Card(rank: .Three, suit: .Spades)
    let threeOfSpadesDescription = threeOfSpades.simpleDescription()