方法是与某些特定类型相关联的函数。类、结构体、枚举都可以定义实例方法；实例方法为给定类型的实例封装了具体的任务与功能。类、结构体、枚举也可以定义类型方法；类型方法与类型本身相关联。类型方法与 Objective-C 中的类方法（class methods）相似。

实例方法

class Counter {
    var count = 0
    func increment() {
        count += 1
    }
    func incrementBy(amount: Int) {
        count += amount
    }
    func reset() {
        count = 0
    }
}

//用点语法调用
let counter = Counter()
counter.increment() // 1
counter.incrementBy(5) // 6
counter.reset() // 0

//方法的局部参数名和外部参数名称
class Counter1 {
    var count: Int = 0
    func incrementBy(amount: Int, numberOfTimes: Int) {
        count += amount * numberOfTimes
    }
    func incrementBy(amount amount: Int,_ numberOfTimes: Int) {
        count += amount * numberOfTimes
    }
}
let counter1 = Counter1()
counter1.incrementBy(5, numberOfTimes: 3) // 15

//修改方法的外部参数名
counter1.incrementBy(amount: 5, 3) //30

//self属性
class Counter2 {
    var count: Int = 0
    
    func increment() {
        self.count += 1
    }
}

//用self消除方法参数 x和实例属性 x 之间的歧义
struct Point {
    var x = 0.0, y = 0.0
    func isToTheRightOfX(x: Double) -> Bool {
        return self.x > x
    }
}
let somePoint = Point(x: 4.0, y:5.0)
if somePoint.isToTheRightOfX(1.0) {
    print("This point is to the right of the line where x == 1.0")
}

//在实例方法中修改值类型
struct Point1 {
    var x = 0.0, y = 0.0
    mutating func moveByX(x deltaX: Double,y deltaY: Double) {
        x += deltaX
        y += deltaY
    }
}
var somePoint1 = Point1(x: 1.0, y: 1.0)
somePoint1.moveByX(x: 3.0, y: 4.0)
print("The point is now at (\(somePoint1.x), \(somePoint1.y))")

//但是不能改变常量类型的值类型
let somePoint11 = Point1(x: 1.0, y: 1.0)
//somePoint11.moveByX(x: 3.0, y: 4.0) //这会报错

//在可变方法中给self赋值
struct Point2 {
    var x = 0.0, y = 0.0
    mutating func moveByX(x deltaX: Double, y deltaY: Double) {
        self = Point2(x: x + deltaX, y: y + deltaY)
    }
}

//枚举可变方法,self设置为统一枚举类型中不同成员
enum TriStateSwitch {
    case Off, Low, High
    mutating func next() {
        switch self {
        case .Off:
            self = Low
        case .Low:
            self = High
        case .High: 
            self = Off
        }
    }
}
var ovenLight = TriStateSwitch.Low
ovenLight.next() // .High
ovenLight.next() // .Off

类型方法

//OC中的类方法,可以用类名直接调用
class SomeClass {
    class func someTypeMethod() {
        //type method implementation goes here
    }
}
SomeClass.someTypeMethod()

struct LevelTracker {
    static var highestUnlockedLevel = 1
    static func unlockLevel(level: Int) {
        if level > highestUnlockedLevel {
            highestUnlockedLevel = level
        }
    }
    static func levelIsUnlocked(level: Int) -> Bool {
        return level <= highestUnlockedLevel
    }
    var currentLevel = 1
    mutating func advanceToLevel(level: Int) -> Bool {
        if LevelTracker.levelIsUnlocked(level) {
            currentLevel = level
            return true
        } else {
            return false
        }
    }
}

class Player {
    var tracker = LevelTracker()
    let playerName: String
    
    init(name: String) {
        playerName = name
    }
    
    func completedLevel(level: Int) {
        LevelTracker.unlockLevel(level + 1)
        tracker.advanceToLevel(level + 1)
    }
}

var player = Player(name: "Tom")
player.completedLevel(1)
print("highest unlocked level is now \(LevelTracker.highestUnlockedLevel)")

player = Player(name: "Beto")
if player.tracker.advanceToLevel(6) {
    print("player is now on level 6")
} else {
    print("level 6 has not yet been unlocked")
}

原文链接,Swift好难理解起来真是,,,费脑,,,

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