Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

iOS Object-Oriented Swift Class Inheritance Creating a Subclass

Aananya Vyas
Aananya Vyas
20,157 Points

it says - super.init isn't called on all paths before returning from initializer

?

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 = 4

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


}

}

let someCar = Car (numberOfSeats  : 5 )

1 Answer

David Papandrew
David Papandrew
8,386 Points

Since the task only asks you to create a new subclass, Car, with a single default store property, you only need minimal code for the subclass. You don't need an initializer, since the new property is set to default value (4) and all other aspects of Car are same as Vehicle.

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
  }
}

// Enter your code below
class Car: Vehicle {
  var numberOfSeats: Int = 4
}

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

If you did want to include a subclass initializer, you could. This code will also pass the challenge. In this case, you set the subclass specific properties FIRST in the initializer, then you call super.init and pass all the inherited properties to that method (see code below).

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

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