用法

letPers =Person()

Pers.eat()

letTeaC =Teacher()

TeaC.teach()

varStd:Student? =Student(name:"70kg", age1:"22岁")

Std?.name = "小刚"

Std?.show()

Std = nil

funceat() {

        print("吃饭")

    }

functeach() {

        print("上课")

        super.eat()

    }

varname:String="小明"{

        willSet(newValue){

            print("新名:\(newValue)")

        }

        didSet{

            print("旧名:\(oldValue)")

        }

    }

    overridefunceat() {

        print("吃了早餐")

    }

   private(set) var weight:String = "70千克"

    funcshow() {

        print("体重\(weight)")

    }

    lazyvarage:String="22岁"

    init(name:String,age1:String) {

        super.init()

        self.weight= name

        self.age= age1

    }

  public  funcshow1()  {

    print("name:\(name), weight:\(weight), age:\(age)")

    }

    deinit {

        self.age=""

        self.name=""

        print("调用了析构函数")

    }