父类的定义

class Person {
    
    //定义类的属性
    var name:String?
    var sex:String = "Female"
    var age:Int?
    var height:Double?
    var weight:Double?
    var nationality:String = "China"
    
    //定义类的方法
    func sleep() {
        print("\(name) sleep")
    }
    
    func eat(food:String) {
        print("\(name) eat \(food)")
    }
    
}

子类的定义

class Student:Person {
    
    var schoolName:String?
    var studentNO:Int?
    
    func study () {
        print("\(name) study in \(schoolName)")
    }
    
    //重写父类的方法
    override func eat(food: String) {
        print("\(name) eat \(food) in \(schoolName)")
    }
}

子类的实例化与操作

//实例化
var student = Student()

//赋值
student.name = "jack"
student.sex = "male"
student.age = 34
student.height = 1.75
student.weight = 65.0
student.schoolName = "MIT"
student.studentNO = 201607061234

//调用父类方法
student.sleep()

//调用子类方法
student.study()

//调用子类重写的方法
student.eat("rice")

运行结果：