class Youtuber: Person {

  let channelName: String
  var subscribers: Int

  //we need to pass in the name & age of the Youtuber Person
  init(channelName: String, subscribers: Int, name: String, age: Int) {
    self.channelName = channelName
    self.subscribers = subscribers

    //we use this to initialise the Person from within the subclass
    super.init(name: String, age: Int)
  }

  /** This will override the celebrateBirthday in the superclass */
  override func celebrateBirthday() {
    self.age += 1
    print("Hi, happy birthday from ur youtube subscribers")
  }

}

Agoi: Person = Person(name: "Adeyemi", age: 27)
Agoi.celebrateBirthday() //Happy birthday Adeyemi


Abel: Youtuber = Youtuber(channelName:"Swift",subscribers:32,name:"Abel",age:27)
Abel.celebrateBirthday() //Hi, happy birthday from ur youtube subscribers