swift 类的动态扩展

import Foundation


class Student{
    func sayHi()
    {
         print("student say hi")
    }

}

extension Student{
    func sayextensionFunc(){
        print("extension func")
    }
}

class Persion:Student{
    
    var _name:String
    
    init(name:String) {
        self._name = name
    }
    
    override func sayHi() {
        super.sayHi()
        print("say \(self._name)")
    }
}

var persion = Persion(name: "yihong")
persion.sayHi()
persion.sayextensionFunc()