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iOS Object-Oriented Swift Class Inheritance Creating a Subclass

mohamed hassan
mohamed hassan
2,079 Points
Posted by mohamed hassan
mohamed hassan
2,079 Points

how to add a property to a subclass ?

I have tried to solve the challenge as the same way of the video however it keeps returning errors after reading some things about inheritance and initializers and how to add into the sub class it never used the override , I tried do it first in the play ground and it went through however here it is nor I need help , I don't know what exactly I did wrong here is my answer In the editor, I have provided a class named Vehicle.

Your task is to create a subclass of Vehicle, named Car, that adds an additional stored property numberOfSeats of type Int with a default value of 4.

Once you've implemented the Car class, create an instance and assign it to a constant named someCar.

objects.swift 
class Vehicle {
  var numberOfDoors: Int
  var numberOfWheels: Int

  init(withDoors doors: Int, andWheels wheels: Int) {
      self.numberOfDoors = doors
      self.numberOfWheels = wheels
  }
class Car: Vehicle {
    var numberOfSeats : Int

     init (withDoors doors: Int, andWheels wheels: Int, numberOfSeats: Int) {

        super.init(withDoors: doors, andWheels: wheels)
        self.numberOfSeats = 4

    }

}
let someCar = Car(withDoors: 4, andWheels: 4, numberOfSeats: 4)
// Enter your code below

1 Answer

Jeremy Conley
Jeremy Conley
16,657 Points
Jeremy Conley
Jeremy Conley
16,657 Points

So since the default value of the new stored property is 4, you don't need to create a new init method for the subclass. Create your new car using the init method from the parent class.

class Vehicle {
  var numberOfDoors: Int
  var numberOfWheels: Int

  init(withDoors doors: Int, andWheels wheels: Int) {
      self.numberOfDoors = doors
      self.numberOfWheels = wheels
  }
}

// Enter your code below

class Car: Vehicle {
  var numberOfSeats = 4
}

let someCar = Car(withDoors: 4, andWheels: 4)
Jeremy Conley
Jeremy Conley
16,657 Points
Jeremy Conley
Jeremy Conley
16,657 Points

However if you did want to initialize your subclass with a certain number of seats, it would look like this

class Vehicle {
    var numberOfDoors: Int
    var numberOfWheels: Int

    init(withDoors doors: Int, andWheels wheels: Int) {
        self.numberOfDoors = doors
        self.numberOfWheels = wheels
    }
}
class Car: Vehicle {
    var numberOfSeats : Int

    init(withDoors doors: Int, andWheels wheels: Int, numberOfSeats: Int) {

        self.numberOfSeats = numberOfSeats
        super.init(withDoors: doors, andWheels: wheels)
    }

}
let someCar = Car(withDoors: 4, andWheels: 4, numberOfSeats: 4)