2020-11-17|2020-11-17 懒加载 lazy 2020-11-17懒加载lazy

//懒加载，lazy语句会在init后执行 class SleepingBeauty {init(){ print("zzz... 沉睡中。。。") //sleep(2) print("睡美人准备好了") } }class Castle { lazy var princess = SleepingBeauty()init() { print("城堡准备好了！") } }print("一座城堡即将出现。。。") let castle = Castle() castle.princess

用懒加载来避免可选型

class ViewController: UIviewController { lazy var label: UILabel = UILabel(frame: .zero)override func loadView(){ super.loadViewself.view.addSubview(self.label) }override func ViewDidLoad() { syper.viewDidLoad()self.label.textColor = .black self.label.font = UIFont.systemFont(ofSize: 16, weight: .bold) } }