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

Maanvir Sidhu
Maanvir Sidhu
3,301 Points
Posted by Maanvir Sidhu
Maanvir Sidhu
3,301 Points

In the editor you've been provided with two classes - Point to represent a coordinate point and Machine. The machine has

I don't get why i am getting compiler error?

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!")
  }
}


class Robot: Machine {
override func move(_ direction: String) {
 switch direction {
    case "Up": location.y ++

    case "Down": location.y --

    case "Left": location.x --

    case "Right": location.x ++

    default: break
        }
}
}

2 Answers

andren
andren
28,558 Points
andren
andren
28,558 Points

The ++ and -- operators are not supported in Swift 3. If you want to increase or decrease a variable using shorthand you have to use += 1 or -= 1 instead, like this:

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!")
  }
}


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
    }
  }
}

Then your code will work.