class Module { let name: String init(name: String) { self.name = name } var sub: SubModule? deinit { print("\(name) 主模块") } } class SubModule { let number: Int init(number: Int) { self.number = number } weak var topic: Module? deinit { print("子模块 topic 数为 \(number)") } } var toc: Module? var list: SubModule? toc = Module(name: "ARC") list = SubModule(number: 4) toc!.sub = list list!.topic = toc toc = nil list = nil