Subclass Challenge Question I cannot get past and feel I'm doing what's asked!

Question

Challenge: 
In the editor you've been provided with two classes - Point to represent a coordinate point and Machine. The machine has a move method that doesn't do anything.
Your task is to subclass Machine and create a new class named Robot. In the Robot class, override the move method and provide the following implementation.
If you enter the string "Up" the y coordinate of the Robot's location increases by 1. "Down" decreases it by 1.
If you enter "Left", the x coordinate of the location property decreases by 1 while "Right" increases it by 1.
Note: If you use a switch statement you can use the break statement in the default clause to exit the current iteration.
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 am a machine!")
  }
}
Here is my answer:
class Robot: Machine {
  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
        }
    }
}
And the error message I keep receiving says "Bummer! For the Up direction make sure the location's y property increases by 1"
I feel like I have retried writing every which way. Please help me move on through this challenge!

Jessica Mylius · Answer

Thank you! I entered "override" before and it was giving me an error, but for some reason it worked today.

Chris Stromberg · Answer

You need to add "override" to your function per the challenge.  I have attached an explanation for why you would use override.
```swift
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 }
}
```
From the Swift Programming Guide
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.

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Jessica Mylius

Jessica Mylius

Subclass Challenge Question I cannot get past and feel I'm doing what's asked!

Jessica Mylius

Jessica Mylius

Chris Stromberg

Chris Stromberg

2 Answers

Chris Stromberg

Chris Stromberg

Jessica Mylius

Jessica Mylius