015_swift_交叉引用和弱引用

class People{
    var name: String
    var pet: Pet?
    init(name:String){
        self.name=name
        print("People is initialized")
        
    }
    deinit {
        print("People is deinitialized")
    }
}
class Pet{
    var name: String
    var master: People?
    init(name:String){
        self.name=name
        print("Pet is initialized")
    }
    deinit {
        print("Pet is deinitalized.")
    }
}
var dot=Pet(name: "Pet")
var master=People(name: "People")
dot.master=master
master.pet=dot
master = nil
dot = nil
//当都设置为空后 并没有执行到析构函数
//因为他们 在互相应用 如何解除这种引用呢 在其中的一个声明上面增加 weak var master: People? 之后就能正常释放了