class Person: NSObject {

 var name: String // 姓名
 var age: Int  // 年龄

 // 构造函数
 init(name: String,age: Int) {
  self.name = name
  self.age = age
  // 必须在 super.init() 之前 初始化对象
  super.init()
 }
}

class Student: Person {

 var lesson: String

 /// 重写
 ///
 /// - Parameters:
 /// - name: 姓名
 /// - age: 年龄
 override init(name: String, age: Int) {

  lesson = "Python" // 必须放在super.init()之前

  super.init(name: name, age: age)

 }
}

 /// 重写实例化的对象
 let s = Student(name: "Joyce", age: 18)
 print(s.lesson) // Python

class Student: Person {

 var lesson: String

 /// 重载
 ///
 /// - Parameters:
 /// - name: 姓名
 /// - age: 年龄
 /// - lesson: 课程
 init(name: String, age: Int, lesson:String) {

  self.lesson = lesson

  super.init(name: name, age: age)
 }

}

 /// 重载实例化的对象
 let s1 = Student(name: "帅哥", age: 21, lesson: "HTML 5")
 print(s1.lesson) // HTML 5