Not sure what I did wrong here!

Question

objects.swift

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: Int = 4

  init(numberOfSeats: Int) {
    self.numberOfSeats = numberOfSeats
     }
  }

  let someCar = Car(numberOfSeats: 4)

Answer 1 · 2017-02-08T21:21:18Z

February 8, 2017 9:21pm

Hi Richard,

Car is a subclass of Vehicle so you have to make sure that you initialize the superclass properties as well. You do this by using by calling super.init() in the subclass designated initializer.

Note that in the subclass designated initializer you must initialize all your subclass properties first and then you call the super.init.

Here is the code:

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 = 4

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

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

Also worth noting that since you have a default value for the Car subclass' only stored property (numberOfSeats), you technically don't need an initializer for the subclass. You could get away with this solution where you simply use the inherited super class initializer when instantiating a new car object.

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 = 4
}

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

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Richard Pitts

Richard Pitts

Not sure what I did wrong here!

1 Answer

David Papandrew

David Papandrew