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iOS Object-Oriented Swift Class Inheritance Creating a Subclass

ali aboutaleb
ali aboutaleb
4,025 Points
Posted by ali aboutaleb
ali aboutaleb
4,025 Points

Cant solve this.. anyone can help??

im having a hard time with this task

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

let someCar = Car(withDoors: 4, andWheels: 4, andSeats: 4)

2 Answers

Heidi Puk Hermann
Heidi Puk Hermann
33,366 Points
Heidi Puk Hermann
Heidi Puk Hermann
33,366 Points

Hi Ali,

you have implemented this part of the task wrong : "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."

you are asked to give a default value of 4 seats to the car class, which means that it should not be in the initializer. Your code should look like this:

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

    override init(withDoors doors: Int, andWheels wheels: Int){
        super.init(withDoors: doors, andWheels: wheels)
    }
}

let someCar = Car(withDoors: 4, andWheels: 4)
sugabelly
sugabelly
2,524 Points

I have a question. Based on your answer, how would you write this code if in the subclass, there was no initial value specified?

i.e. instead of the Car having a default numberOfSeats of 4, it's just of type Int. In that case, how would you initialise that in the code you wrote above? Do you use init? If so, how?

Heidi Puk Hermann
Heidi Puk Hermann
33,366 Points
Heidi Puk Hermann
Heidi Puk Hermann
33,366 Points

in that case your initializer would look like this: 

class Car: Vehicle {
    var numberOfSeats: Int

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

When the variable has been given an initial value, you do not need to include it in the initializer, since it is all ready initialized.

Hope it makes sence :)