agoiabel

class Person {
  let name: String
  var age: Int
  
  init(name: String, age: Int) {
    self.name = name
    self.age = age
  }
  func celebrateBirthday() {
    self.age += 1

agoiabel

Abel: Youtuber = Youtuber(channelName:"Swift",subscribers:32,name:"Abel",age:27)

Abel.celebrateBirthday() //Happy birthday Abel

Abel.age //27

agoiabel

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
    

agoiabel

class Person {
  var name: String
  var gender: String = "Male"
  
  init(name: String) {
    self.name = name
  }
}

class Foreigner: Person {

agoiabel

Person {
  var firstname: String
  var middlename: String
  var lastname: String
}

//this will definitely work because i have a middlename
let me = Person(firstname: "Abel", middlename: "abel", lastname: "Adeyemi")

//This will throw an error

agoiabel

Person {
  var firstname: String
  var middlename: String? //we created the optional with the ?
  var lastname: String
  
  func fullName() -> () {
     print("Your fullname is \(firstname) \(middlename!) \(lastname)")
  }
}

agoiabel

Person {
  var firstname: String
  var middlename: String?
  var lastname: String
  
  func fullName() -> () {
     print("Your fullname is \(firstname) \(middlename!) \(lastname)")
  }
}

agoiabel

Person {
  var firstname: String, var middlename: String?, var lastname: String
  
  func fullName() -> () {
     if (middlename != nil) {
        print("Your fullname is \(firstname) \(middlename!) \(lastname)")  
     } else {
        print("Your fullname is \(firstname) \(lastname)")
     }
     

agoiabel

Person {
  var firstname: String, var middlename: String?, var lastname: String
  
  func fullName() -> () {
    
     if let middlename: String = middlename {
         print("Your fullname is \(firstname) \(middlename) \(lastname)")
     } else {
         print("Your fullname is \(firstname) \(lastname)")
     }

agoiabel

Person {
  var firstname: String, var middlename: String?, var lastname: String
  
  func fullName() -> () {
    
     guard let middlename = middlename else {
       print("Your fullname is \(firstname) \(lastname)")  
       return
     }