--- /dev/null
+//: [Previous](@previous)
+
+import Foundation
+
+var str = "Hello, playground"
+
+//: [Next](@next)
+
+class Counter {
+ var count = 0
+
+ func increment() {
+ count += 1
+ }
+
+ func increment(by amount: Int) {
+ count += amount
+ }
+
+ func reset() {
+ count = 0
+ }
+}
+
+var counter = Counter()
+
+counter.increment()
+print(counter.count)
+counter.increment(by: 100)
+print(counter.count)
+counter.reset()
+print(counter.count)
+
+struct Point {
+ var x = 0.0, y = 0.0
+ // 结构体和枚举是值类型。默认情况下，值类型的属性不能在它的实例方法中被修改，如果要修改将关键字mutating 放到方法的func关键字之前
+ mutating func move(x deltaX: Double, y deltaY: Double) {
+ self.x += deltaX
+ self.y += deltaY
+ }
+
+ // 可变方法能够赋给隐含属性self一个全新的实例
+ mutating func moveTo(x deltaX: Double, y deltaY: Double) {
+ self = Point(x: deltaX, y: deltaY)
+ }
+ var description: String {
+ get {
+ return "Point(\(x), \(y))"
+ }
+ }
+}
+
+
+var point = Point()
+print(point.description)
+point.move(x: 1, y: 7)
+print(point.description)
+point.move(x: 8, y: 4)
+print(point.description)
+point.moveTo(x: 9, y: 9)
+print(point.description)
+
+
+// 枚举的可变方法可以把self设置为同一枚举类型中不同的成员
+enum TriStateSwitch: String {
+ case Off
+ case Low
+ case High
+
+ mutating func next() {
+ switch self {
+ case .Off:
+ self = .Low
+ case .Low:
+ self = .High
+ case .High:
+ self = .Off
+ }
+ }
+
+ var description: String {
+ return "Current State: \(self.rawValue)"
+ }
+}
+
+var ovenLight = TriStateSwitch.High
+print(ovenLight.description)
+ovenLight.next()
+print(ovenLight.description)
+ovenLight.next()
+print(ovenLight.description)
+ovenLight.next()
+print(ovenLight.description)
+
+// 类型方法
+class SomeClass {
+ // static & class 加在func前都是定义类型方法的关键字
+ // 不同的是static的不能被子类重写该方法
+ // 而class则可以
+ static func descV1() -> String {
+ return "BaseDescV1"
+ }
+ class func descV2() -> String {
+ return "BaseDescV2"
+ }
+}
+
+class SomeDerivedClass: SomeClass {
+ /*
+ 取消注释会编译错误
+ override static func descV1() -> String {
+ return "BaseDescV1"
+ }
+ */
+ override class func descV2() -> String {
+ return "DerivedDescV2"
+ }
+}
+
+print(SomeClass.descV1())
+print(SomeClass.descV2())
+print(SomeDerivedClass.descV1())
+print(SomeDerivedClass.descV2())
+
+
+class 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
+ }
+
+ @discardableResult // 可以忽略返回值，不会产生警告
+ func advance(to level: Int) -> Bool {
+ if LevelTracker.isUnlocked(level) {
+ currentLevel = level
+ return true
+ } else {
+ return false
+ }
+ }
+}
+
+class Player {
+ var tracker = LevelTracker()
+ let playerName: String
+
+ init(name: String) {
+ self.playerName = name
+ }
+
+ func complete(level: Int) {
+ LevelTracker.unlock(level)
+ tracker.advance(to: level)
+ }
+}
+
+
+var player = Player(name: "Ace")
+player.complete(level: 1)
+player.complete(level: 2)
+if player.tracker.advance(to: 3) {
+ print("player is now on level 3")
+} else {
+ print("level 3 has not yet been unlocked")
+}
+player.complete(level: 3)
+if player.tracker.advance(to: 3) {
+ print("- player is now on level 3")
+} else {
+ print("- level 3 has not yet been unlocked")
+}
dataManager.importer
-
printLine("Computed Properties")
struct Point {
var origin = Point()
var size = Size()
+ // 必须使用 var 关键字定义计算属性，包括只读计算属性，因为它们的值不是固定的
var center: Point {
get {
var p = Point()
}
/*
- //set 有更简洁的写法，set重命名参数的话默认参数名为newValue
+ //set 有更简洁的写法，set重命名参数的话默认参数名为newValue
set {
origin.x = newValue.x - size.width/2
let fourByFiveByTwo = Cuboid(width:4.0, height:5.0, depth:2.0)
print(fourByFiveByTwo.volume)
+
+
+// 属性观察器
+class StepCounter
+{
+ var totalSteps: Int = 0 {
+ // 默认的分别是newValue & oldValue
+ willSet(newValue) {
+ print("About to set totalSteps to \(newValue)")
+ }
+
+ didSet {
+ if totalSteps > oldValue {
+ print("Added \(totalSteps-oldValue) steps")
+ }
+ }
+ }
+
+ var serialNumber: String = "0000-00000-0000000-000" {
+ // 不想用newValue & oldValue 可以命名为别的方法
+ willSet(newSerialNumber) {
+ print("New serial number \(newSerialNumber)")
+ }
+
+ didSet(oldSerialNumber) {
+ print("Old serial number \(oldSerialNumber)")
+ }
+ }
+}
+
+
+let stepCounter = StepCounter()
+
+stepCounter.totalSteps = 100
+stepCounter.totalSteps = 300
+stepCounter.totalSteps = 657
+stepCounter.totalSteps = 257
+stepCounter.serialNumber = "0010-23873-83F123A-ECA"
+stepCounter.serialNumber = "10A0-8376C-247232E-EST"
+
+
+// 类型属性
+struct SomeStructure {
+ static var storedType = "Structure"
+ static var computedType: Int {
+ return 1;
+ }
+}
+
+enum SomeEnumeration {
+ static var v: String = "ComputedEnumeration"
+ static var storedType = "Enumeration"
+ static var computedType: String {
+ get {
+ return "get" + v
+ }
+
+ set(v) {
+ self.v = v
+ }
+ }
+}
+
+class SomeClass {
+ static var storedType = "Class"
+ static var computedType: String {
+ return "ComputedClass"
+ }
+}
+
+print(SomeStructure.storedType)
+print(SomeEnumeration.storedType)
+print(SomeClass.storedType)
+
+print(SomeStructure.computedType)
+print(SomeEnumeration.computedType)
+SomeEnumeration.computedType = "ComputedEnumerationV2"
+print(SomeEnumeration.computedType)
+print(SomeClass.computedType)
+