Swift 方法

实例方法

import UIKit

// 实例方法
class Counter {
    var count = 0
    func increment() {
        count += 1
    }
    
    func increment(amount: Int) {
        count += amount
    }
    
    func reset() {
        count = 0
    }
}

let counter = Counter()
counter.increment()
print(counter.count)
counter.increment(5)
print(counter.count)
counter.reset()
print(counter.count)

console log 如下

实例方法.png

mutating 关键字的使用
注意:结构体和枚举都是值拷贝，默认不能修改实例值，如果要修改方法前面需要加上 mutating 关键字

// mutating 关键字的使用
struct Point {
    var x = 0.0, y = 0.0
    mutating func moveBy(deltaX: Double, deltaY: Double) {
        x += deltaX
        y += deltaY
    }
    
    mutating func moveTwo(deltaX: Double, deltaY: Double) {
        self = Point(x: x + deltaX, y: y + deltaY)
    }
}

var somePoint = Point(x: 1.0, y: 1.0)
somePoint.moveBy(2.0, deltaY: 3.0)
print("The point is now at (\(somePoint.x), \(somePoint.y))")

somePoint.moveTwo(3.0, deltaY: 4.0)
print("The point is now at (\(somePoint.x), \(somePoint.y))")

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.off
ovenLight.next()
if ovenLight == TriStateSwitch.low {
    print("ovenLight now is low")
}
ovenLight.next()
if ovenLight == TriStateSwitch.high {
    print("ovenLight now is high")
}

console log 如下

mutating 关键字的使用.png

类方法 --用class 关键字声明

// 类方法
class SomeClass {
    class func someTypeMethod(){
        print("SomeClass type method.")
    }
}

SomeClass.someTypeMethod()

console log 如下

类方法.png

实战

// 方法实战
struct LevelTracker {
    static var highestUnlockedLevel = 1
    var currentLevel = 1
    
    static func unlock(level: Int) {
        if level > highestUnlockedLevel {
            highestUnlockedLevel = level
        }
    }
    
    static func isUnlocked(level: Int) -> Bool {
        return level < highestUnlockedLevel
    }
    
    mutating func advance(level: Int) -> Bool {
        if LevelTracker.isUnlocked(level) {
            currentLevel = level
            return true
        } else {
            return false
        }
    }
}

class Player {
    var tracker = LevelTracker()
    let playerName: String
    func complete(level: Int) {
        LevelTracker.unlock(level + 1)
        tracker.advance(level + 1)
    }
    
    init(name: String){
        playerName = name
    }
}

var player = Player(name: "Argyrios")
player.complete(1)

print("highest unlocked level is now \(LevelTracker.highestUnlockedLevel)")

player = Player(name: "Beto")
if player.tracker.advance(5) {
    print("player is now on level 5")
} else {
    print("level 5 has not yet been unlocked")
}

console log 如下

方法实战.png