本文內(nèi)容來自The Swift Programming Language 中文版

Tips

Swift 并不強(qiáng)制要求你在每條語句的結(jié)尾處使用分號(hào)

變量常量聲明

var myVariable:Int;
myVariable = 13;
let myConstant:Int = 13;
let emptyArray = [String]()
let emptyDictionary = [String: Float]()

控制流

1.使用if和switch來進(jìn)行條件操作，使用for in、for、while和repeat while來進(jìn)行循環(huán)
2.swift使用..<來表示范圍，..<的意思是<,...的意思是<=
比如

var firstForLoop = 0
for i in 0..<4 {
    firstForLoop += i
}
print(firstForLoop)

函數(shù)和閉包

函數(shù)：使用func來聲明一個(gè)函數(shù)，使用名字和參數(shù)來調(diào)用函數(shù)。使用->來指定函數(shù)返回值的類型
普通例子：

func greet(name: String, day: String) -> String {
    return "Hello \(name), today is \(day)."
}
greet("Bob", day: "Tuesday")

返回類型為元組(函數(shù)返回多個(gè)值)：

func calculateStatistics(scores: [Int]) -> (min: Int, max: Int, sum: Int) {
    var min = scores[0]
    var max = scores[0]
    var sum = 0

    for score in scores {
        if score > max {
            max = score
        } else if score < min {
            min = score
        }
        sum += score
    }

    return (min, max, sum)
}
let statistics = calculateStatistics([5, 3, 100, 3, 9])
print("statistics.sum:\(statistics.sum)")//120
print("statistics.1(max):\(statistics.1)")//100
print("statistics.0(min):\(statistics.0)")//3

函數(shù)可以帶有可變個(gè)數(shù)的參數(shù)，這些參數(shù)在函數(shù)內(nèi)表現(xiàn)為數(shù)組的形式：

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

函數(shù)可以作為返回值（return Int -> Int不理解，不是return func？ ）

func makeIncrementer() -> (Int -> Int) {
    func addOne(number: Int) -> Int {
        return 1 + number
    }
    return addOne
}
var increment = makeIncrementer()
increment(7)

函數(shù)實(shí)際上是一種特殊的閉包:它是一段能之后被調(diào)取的代碼。閉包中的代碼能訪問閉包所建作用域中能得到的變量和函數(shù)，即使閉包是在一個(gè)不同的作用域被執(zhí)行的 - 你已經(jīng)在嵌套函數(shù)例子中所看到。你可以使用{}來創(chuàng)建一個(gè)匿名閉包。使用in將參數(shù)和返回值類型聲明與閉包函數(shù)體進(jìn)行分離。

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

更簡(jiǎn)潔的寫法（單個(gè)語句閉包會(huì)把它語句的值當(dāng)做結(jié)果返回）

let mappedNumbers = numbers.map({ number in 3 * number })
print(mappedNumbers)

類（Class）

1.類的聲明

class Shape {
    var numberOfSides = 0
    func simpleDescription() -> String {
        return "A shape with \(numberOfSides) sides."
    }
}

2.類的實(shí)例化

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

3.類的構(gòu)造方法

class NamedShape {
    var numberOfSides: Int = 0
    var name: String

    init(name: String) {
        self.name = name
    }

    func simpleDescription() -> String {
        return "A shape with \(numberOfSides) sides."
    }
}

1.用self關(guān)鍵字來區(qū)別實(shí)例變量
2.如果你需要在刪除對(duì)象之前進(jìn)行一些清理工作，使用deinit創(chuàng)建一個(gè)析構(gòu)函數(shù)
子類的定義方法是在它們的類名后面加上父類的名字，用冒號(hào)分割，比如
class Square: NamedShape
子類如果要重寫父類的方法的話，需要用override標(biāo)記

4.類屬性的getter跟setter

class EquilateralTriangle: NamedShape {
    var sideLength: Double = 0.0

    init(sideLength: Double, name: String) {
        self.sideLength = sideLength
        super.init(name: name)
        numberOfSides = 3
    }

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

    override func simpleDescription() -> String {
        return "An equilateral triagle with sides of length \(sideLength)."
    }
}
var triangle = EquilateralTriangle(sideLength: 3.1, name: "a triangle")
print(triangle.perimeter)
triangle.perimeter = 9.9
print(triangle.sideLength)

在perimeter的 setter 中，新值的名字是newValue。你可以在set之后顯式的設(shè)置一個(gè)名字,諸如set(_perimeter:Double) { sideLength = newValue / 3.0}

枚舉跟結(jié)構(gòu)體

1.初始化枚舉

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.rawValue)
                }
            }
        }
        let ace = Rank.Ace
        print(ace)//Ace
        let aceRawValue = ace.rawValue
        print(aceRawValue)//1
        let aceDescription = ace.simpleDescription()
        print(aceDescription)//ace

2.使用struct來創(chuàng)建一個(gè)結(jié)構(gòu)體。結(jié)構(gòu)體和類有很多相同的地方，比如方法和構(gòu)造器。它們之間最大的一個(gè)區(qū)別就是結(jié)構(gòu)體是傳值，類是傳引用

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

協(xié)議和擴(kuò)展

1.使用protocol來聲明一個(gè)協(xié)議

protocol ExampleProtocol {
    var simpleDescription: String { get }
    mutating func adjust()
}

2.類、枚舉和結(jié)構(gòu)體都可以實(shí)現(xiàn)協(xié)議

class SimpleClass: ExampleProtocol {
    var simpleDescription: String = "A very simple class."
    var anotherProperty: Int = 69105
    func adjust() {
        simpleDescription += "  Now 100% adjusted."
    }
}
var a = SimpleClass()
a.adjust()
let aDescription = a.simpleDescription

struct SimpleStructure: ExampleProtocol {
    var simpleDescription: String = "A simple structure"
    mutating func adjust() {
        simpleDescription += " (adjusted)"
    }
}
var b = SimpleStructure()
b.adjust()
let bDescription = b.simpleDescription

3.使用extension來為現(xiàn)有的類型添加功能

extension Int: ExampleProtocol {
    var simpleDescription: String {
        return "The number \(self)"
    }
    mutating func adjust() {
        self += 42
    }
}
print(7.simpleDescription)//The number 7