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

Michel Ortega
Michel Ortega
2,279 Points
Posted by Michel Ortega
Michel Ortega
2,279 Points

What am I missing?

It seems that theres a problem with my Robot subclass. Can you please tell me what it is and how to avoid it next time. I feel's like im almost there learning the polymorphism practice and theory. SOS

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! Im a machine!")
  }
}

// Enter your code below

class Robot: Machine{

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

  override func move(_ direction: String){

    switch direction{

        case "Up":
            self.y += 1

        case "Left":
            self.x += 1
        default:
            break

        }
  }

}

2 Answers

Reed Carson
Reed Carson
8,306 Points
Reed Carson
Reed Carson
8,306 Points

In your switch statement you are referring to a "self.y" and "self.x". Neither Robot or Machine class has a property named 'x' or 'y', but the class Point does. Robot's property 'location' is of type Point, and its the 'x' and 'y' properties of 'location' that you are trying to change. I bet you can take it from here. The answer is at the bottom if you can't figure it out.

also you don't need to override the init because you aren't changing it.

**spoiler answer below*** **

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self.x needs to be location.x and self.y needs to be location.y

Michel Ortega
Michel Ortega
2,279 Points
Michel Ortega
Michel Ortega
2,279 Points

Thanks a lot Reed. Now I see things more clearly and I think I do get it now, thanks to you. Again, thanks a lot. xoxo