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

Why is my code wrong???

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.

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 am a machine!")
  }
}

// Enter your code below

class Robot: Machine {
  super.init() 
}

override func move(_ direction: String) { 
  var 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 
  }
}
}

1 Answer

Victor Mercier
MOD
Victor Mercier
Treehouse Moderator 13,884 Points

Hi, mitchellwan so there is two things not working in your code :

The first thing is that when you are overriding the move method, you need to do it in the body of the sub class, otherwise, the compiler is not able to figure out what you want to override.

The second thing is that you do not need to create another local constant named direction, because you already have an an argument (local name) representing the direction.

So, here is the code that will work:

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
    }
  }
}

If that helped you, please mark as best answer to indicate that your issue is resolved!

Hey, Victor, got it, thanks a lot! :)