- 计算型属性
struct Point {
var x = 0.0
var y = 0.0
}
struct Size {
var width = 0.0
var height = 0.0
}
class Rectangle {
var origin = Point()
var size = Size()
//计算型属性必须声明为var
var center: Point {
// getter和setter方法
get {
let centerX = origin.x + size.width / 2
let centerY = origin.y + size.height / 2
return Point(x: centerX, y: centerY)
}
set {
origin.x = newValue.x - size.width / 2
origin.y = newValue.y - size.height / 2
}
}
init(origin: Point, size: Size) {
self.origin = origin
self.size = size
}
//如果只是取值，直接return即可
var area: Double {
return size.height * size.width
}
}
var rec = Rectangle(origin: Point(), size: Size(width: 10, height: 10))
//使用get方法获取属性值
rec.center
//使用set方法修改center坐标
rec.center = Point()
- 类型属性（全局属性）
lass Player {
var name: String
var totalScore = 0
//全局变量，针对所有对象
static var highestScore = 0
init(name: String) {
self.name = name
}
func play() {
let score = Int(arc4random() % 100)
print("\(name) played and got \(score) scores")
totalScore += score
if totalScore > Player.highestScore {
Player.highestScore = totalScore
}
print("The total score is \(totalScore)")
print("The highest score is \(Player.highestScore)")
}
}
var player1 = Player(name: "player1")
player1.play()
player1.play()
var player2 = Player(name: "player2")
player2.play()
player2.play()
- 类型方法（全局方法）
struct Matrix {
var m: [[Int]]
var row: Int
var col: Int
init?(arr2d: [[Int]]) {
guard arr2d.count > 0 else {
return nil
}
let row = arr2d[0].count
let col = arr2d.count
for i in 1 ..< col {
if arr2d[i].count != row {
return nil
}
}
self.m = arr2d
self.row = row
self.col = col
}
func printMatrix(){
for i in 0 ..< col {
for j in 0 ..< row {
print(m[i][j], terminator: " ")
}
print()
}
}
//通过类型方法创建多阶的单位矩阵模版
static func identityMatrix(n: Int) -> Matrix? {
if n <= 0 {
return nil
}
var arr: [[Int]] = []
for i in 0 ..< n {
var row = [Int](repeatElement(0, count: n))
row[i] = 1
arr.append(row)
}
return Matrix(arr2d: arr)
}
}
if let arr2d = Matrix(arr2d: [[2,3], [4,5], [3, 4]]) {
arr2d.printMatrix()
}
if let arr = Matrix.identityMatrix(n: 3) {
arr.printMatrix()
}
- 属性观察器
class LightBulb {
static let maxCurrent = 30
var current = 0 {
//didSet关键字，还有willSet关键字
didSet {
if current == LightBulb.maxCurrent {
print("Pay attetion! the current value get to the maxium point")
}
else if current > LightBulb.maxCurrent {
print("The temp is too high!")
current = oldValue
print("The current is \(current)")
}
}
}
}
let bulb = LightBulb()
bulb.current = 20
bulb.current = 30
bulb.current = 80
//Pay attetion! the current value get to the maxium point
//The temp is too high!
//The current is 30
//另一个例子
enum Theme {
case DayMode
case NightMode
}
class UI {
var fontColor: UIColor!
var backgroundColor: UIColor!
var themeMode: Theme {
didSet {
changeTheme(themeMode: themeMode)
// switch themeMode {
// case .DayMode:
// fontColor = UIColor.red
// backgroundColor = UIColor.red
// case .NightMode:
// fontColor = UIColor.black
// backgroundColor = UIColor.black
// }
}
}
init(themeMode: Theme) {
self.themeMode = themeMode
changeTheme(themeMode: themeMode)
// switch themeMode {
// case .DayMode:
// fontColor = UIColor.red
// backgroundColor = UIColor.red
// case .NightMode:
// fontColor = UIColor.black
// backgroundColor = UIColor.black
// }
}
func changeTheme(themeMode: Theme) {
switch themeMode {
case .DayMode:
fontColor = UIColor.red
backgroundColor = UIColor.red
case .NightMode:
fontColor = UIColor.black
backgroundColor = UIColor.black
}
}
}
let ui = UI(themeMode: .DayMode)
ui.backgroundColor
ui.fontColor
ui.themeMode = .NightMode //该属性被赋值时才会开始调用didset方法体
ui.backgroundColor
ui.fontColor
