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iOS Object-Oriented Swift Value vs Reference Types Final Challenge

Posted by Jesse Price
Jesse Price
Courses Plus Student 14,333 Points

Object-Oriented Swift Code Challenge: Final Challenge

I think I'm OK with the first class, but I'm stumped at initializing the Car class.

Vehicle.swift 
class Vehicle {
    let wheels: Int
    let doors: Int

    // Designated initializer
    init(wheels:Int, doors:Int){
        self.wheels = wheels
        self.doors = doors
    }
}

class Car: Vehicle {
    // A car must default to 4 wheels and 4 doors
    init(wheels: Int, doors: Int){
      //call super.init

    }
}

3 Answers

truemaulik
truemaulik
Courses Plus Student 7,765 Points

most welcome! No it is not used to override a function. To override a function, we just use the override keyword before the function we want to override:

override func()

"_" is used because we want to give initial values to the parameters (wheels & doors) in the init declaration :

init( _ wheels: Int = 4, _ doors: Int = 4)

More Extra & helpful explanation in detail: If we are giving initial values to the parameters in the block of init(), there is no need to add "_" before parameter names :

init(wheels: Int, _doors: Int) {
wheels = 4
doors = 4
super.init(wheels: wheels, doors: doors)
}

But if we do like this, then we have initialised wheels and doors inside the init() code block, but in our program, wheels and doors are defined as constants

let wheels: Int
let doors: Int

But adding the "_" before the parameter name is the best practice, so we should follow it.

I would recommend you to watch the videos in that stage again, it will help you in better understanding.

I hope this would help :) Thanks

truemaulik
PLUS
truemaulik
Courses Plus Student 7,765 Points
truemaulik
truemaulik
Courses Plus Student 7,765 Points

Here is the answer

class Vehicle {
    let wheels: Int
    let doors: Int

    // Designated initializer
    init(wheels:Int, doors:Int){
        self.wheels = wheels
        self.doors = doors
    }
}

class Car: Vehicle {
    // A car must default to 4 wheels and 4 doors
    init(_ wheels: Int = 4,_ doors: Int = 4){
      // call super.init
      super.init(wheels: wheels, doors: doors)
    }
}
Jesse Price
PLUS
Jesse Price
Courses Plus Student 14,333 Points
Jesse Price
Jesse Price
Courses Plus Student 14,333 Points

Thanks!

Why the " _ " ? The only other time I saw this was to override a function.

Forgive any ignorance on my part, I looked at a line of code for the first time six months ago so this is all very new to me.

Thanks again.