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iOS Object-Oriented Swift 2.0 Class Inheritance Creating a Subclass

Dhruv Mittal
Dhruv Mittal
932 Points
Posted by Dhruv Mittal
Dhruv Mittal
932 Points

Code Challenge: How to initialise new properties in subclasses

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.

classes.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 {
  let isDifferent: Bool = true 
  let numberOfSeats: Int = 4 
  override init(withDoors: Int, andWheels: Int){
    super.init(withDoors: 4, andWheels: 5)
  }
}

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

2 Answers

Moritz Lang
Moritz Lang
25,909 Points
Moritz Lang
Moritz Lang
25,909 Points

Hi, in Car's initializer you hardcoded the values of withDoors & andWheels. You have to use the values passed through the init method instead. If the task is to add more parameters to the initializer, you just have to separat them by a comma and initialize them inside the method.

Dhruv Mittal
Dhruv Mittal
932 Points
Dhruv Mittal
Dhruv Mittal
932 Points

Thank you for the reply, however, I am not sure where or how to initialise the numberOfSeats constant

Could you expand on that?

Moritz Lang
Moritz Lang
25,909 Points
Moritz Lang
Moritz Lang
25,909 Points

You can write it like this:

init(withDoors: Int, andWheels: Int, numberOfSeats: Int){
    super.init(withDoors: 4, andWheels: 5)
    self.numberOfSeats = numberOfSeats
}

However then you'd have to declare numberOfSeats as a variable instead. In my oppinion the est solution would be to declare numberOfSeats as a constant and set a default value in the init method.

Dhruv Mittal
Dhruv Mittal
932 Points
Dhruv Mittal
Dhruv Mittal
932 Points

Thank you for the help!