这篇文章主要介绍“swift的类属性作用是什么”，在日常操作中，相信很多人在swift的类属性作用是什么问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答”swift的类属性作用是什么”的疑惑有所帮助！接下来，请跟着小编一起来学习吧！
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//延迟存储属性 lazy
class DataImporter {
var fileName = "data.txt"
init() {
print("DataImporter inits")
}
}
class DataManager {
lazy var importer = DataImporter()
var data = [String]()
}
let manager = DataManager()
manager.data.append("Some data")
manager.data.append("Some more data")
print("manager.data.append finish")
//manager.data.append finish
print(manager.importer.fileName)
/*
DataImporter inits
data.txt
*///计算属性
struct Point {
var x = 0.0, y = 0.0
}
struct Size {
var width = 0.0, height = 0.0
}
struct Rect {
var origin = Point()
var size = Size()
var center: Point {
get {
Point(x: origin.x + (size.width / 2), y: origin.y + (size.height / 2))
}
set {
origin.x = newValue.x - (size.width / 2)
origin.y = newValue.y - (size.height / 2)
}
}
}
let rect = Rect(origin: Point(x: 2, y: 2), size: Size(width: 4, height: 4))
print(rect.center)
//Point(x: 4.0, y: 4.0)//属性观察者 willSet & didSet
class StepCounter {
var totalSteps: Int = 0 {
//在值被存储之前调用
willSet(newTotalSteps) {
print("About to set totalSteps to \(newTotalSteps)")
}
//在新值在存储之后调用
didSet {
if totalSteps > oldValue {
print("Added \(totalSteps - oldValue) step")
}
}
}
}
let stepCounter = StepCounter()
stepCounter.totalSteps = 200
stepCounter.totalSteps = 360
stepCounter.totalSteps = 456
/*
About to set totalSteps to 200
Added 200 step
About to set totalSteps to 360
Added 160 step
About to set totalSteps to 456
Added 96 step
*///类型属性
class SomeClass {
static var storedTypeProperty = "Some Value."
static var computedTypeProperty: Int {
return 27
}
}
print(SomeClass.storedTypeProperty)
//Some Value.到此，关于“swift的类属性作用是什么”的学习就结束了，希望能够解决大家的疑惑。理论与实践的搭配能更好的帮助大家学习，快去试试吧！若想继续学习更多相关知识，请继续关注创新互联网站，小编会继续努力为大家带来更多实用的文章！