《从零开始学Swift》学习笔记（Day 47）——final关键字

final class Person { //声明为final，说明它是不能被继承的 
    var name: String   
    final var age: Int    //定义的age属性  
    final func description() -> String {  //定义description实例方法
        return "(name) 年龄是: (age)"
    }   
    final class func printClass() ->() {  //定义printClass静态方法
        print( "Person 打印...")
    }   
    init (name: String, age: Int) {
        self.name = name
        self.age  = age
    }
}
class Student: Person {                            //编译错误

    var school: String  

    convenience init() {
        self.init(name: "Tony", age: 18, school: "清华大学")
    }  

    init (name: String, age: Int, school: String) {
        self.school = school
        super.init(name: name, age: age)
    }  

    override func description() -> String {         //编译错误    //试图重写description实例方法
        print("父类打印 (super.description())")
        return "(name) 年龄是: (age), 所在学校: (school)。"
    }  

    override class func printClass() ->() {      //编译错误  //试图重写printClass静态方法
        print( "Student 打印...")
    }  

    override var age: Int {                        //编译错误 //试图重写age属性
    get {
        return super.age
    }
    set {
        super.age = newValue < 8 ? 8: newValue
    }
    }
}