方法(Methods)

方法概念：

函数在类，结构体，枚举中就叫方法。

实例方法举例：

class Counter {
   var count = 0
  func increment() {
       count += 1
  }
  func incrementBy(amount: Int) {
      count += amount
}
func reset() {
       count = 0
}
}```
#####实例方法需要实例来调用如通过counter 实例调用Counter类中的increment，incrementBy，reset三个方法

let counter = Counter()
// the initial counter value is 0
counter.increment()
// the counter's value is now 1
counter.incrementBy(5)
// the counter's value is now 6
counter.reset()
// the counter's value is now 0```

Mutating关键字

Swift通过Mutating关键字修改实例方法中的值类型数据，例如在moveByX方法前面加上mutating 修改Point中的x和y的值

struct Point {
    var x = 0.0, y = 0.0
    mutating func moveByX(deltaX: Double, y deltaY: Double) {
    x += deltaX
    y += deltaY
   }
 }
 var somePoint = Point(x: 1.0, y: 1.0)
 somePoint.moveByX(2.0, y: 3.0)
 print("The point is now at (\(somePoint.x), \(somePoint.y))")
 // Prints "The point is now at (3.0, 4.0)"```
####类型方法
#####类型方法有两种关键字:static和class，class关键字表示该方法在子类中可以重写覆盖。在swift中类、结构体、枚举都有类型方法。

class SomeClass {
class func someTypeMethod() {
// type method implementation goes here
}
}
SomeClass.someTypeMethod()```

类型方法只能访问静态变量（在该变量前也有static关键字修饰的变量）实例方法前面加上mutating 关键字以后可以访问静态变量和实例变量

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 关键字访问实例变量
       mutating func advanceToLevel(level: Int) -> Bool {
            if LevelTracker.levelIsUnlocked(level) {
                       currentLevel = level
                       return true
              } else {
                      return false
         }
     }
 }```
####init方法
#####通过init初始化类中的变量

class Player {
let playerName: String
init(name: String) {
playerName = name
}
}
var player = Player(name: "Argyrios")
Print(player.playerName)```