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iOS Build a Simple iPhone App with Swift Getting Started with iOS Development Swift Recap Part 2

Posted by Mitch Little
Mitch Little
11,870 Points

What Do I Execute In the Switch Statement?

I have tried various identifiers to be executed on in the switch statement however I cannot figure it out. The value switched on may also be incorrect.

Thank you for any replies :)

robots.swift 
class Point {
  var x: Int
  var y: Int

  init(x: Int, y: Int) {
    self.x = x
    self.y = y
  }
}

class Machine {
  var location: Point

  init() {
    self.location = Point(x: 0, y: 0)
  }

  func move(_ direction: String) {
    print("Do nothing! I\'m a machine!")
  }
}

// Enter your code below

class Robot: Machine {

  override init() {
    super.init()
  }

  override func move(_ direction: String) {
    switch direction {
      case "Up": 
      case "Down":
      case "Right":
      case "Left": 
      default: break
    }
  }
}

5 Answers

Jeff McDivitt
Jeff McDivitt
23,970 Points
Jeff McDivitt
Jeff McDivitt
23,970 Points

Hi Mitch -

You are switching on the proper value and you have the case values correct also. The instructions state you need to either increase or decrease by 1 for each switch value. That means that the location will change so that needs to be is your switch statement. You also do not need the override init and super init.

class Robot: Machine {

    override func move(_ direction: String) {
        switch direction {
        case "Up":
            location.y += 1
        case "Down":
            location.y -= 1
        case "Left":
            location.x -= 1
        case "Right":
            location.x += 1
        default:
            break
        }
    }
}
Mitch Little
Mitch Little
11,870 Points
Mitch Little
Mitch Little
11,870 Points

Great, really appreciate your help! I just forgot to add the binary operator!

If you have a moment, could you please explain why I do not need to override the init and super init? I thought that if a subclass was called the superclass had to also be initialised first, hence why I included the init method.

Thanks again for your help!

Jeff McDivitt
Jeff McDivitt
23,970 Points
Jeff McDivitt
Jeff McDivitt
23,970 Points

From Apple Docs

Overriding

A subclass can provide its own custom implementation of an instance method, type method, instance property, type property, or subscript that it would otherwise inherit from a superclass. This is known as overriding.

To override a characteristic that would otherwise be inherited, you prefix your overriding definition with the override keyword. Doing so clarifies that you intend to provide an override and have not provided a matching definition by mistake. Overriding by accident can cause unexpected behavior, and any overrides without the override keyword are diagnosed as an error when your code is compiled.

The override keyword also prompts the Swift compiler to check that your overriding class’s superclass (or one of its parents) has a declaration that matches the one you provided for the override. This check ensures that your overriding definition is correct.

Also more information here if needed

https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Initialization.html

Mitch Little
Mitch Little
11,870 Points
Mitch Little
Mitch Little
11,870 Points

Okay thank you :) So essentially it is used when modifying the initialiser in the subclass and when doing so, super.init must be used to provide values to the super class to also initialise it?