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

Posted by Sophia Chiang
Sophia Chiang
736 Points

why is Robot method throwing an error

swift_lint.swift:45:1: error: expected declaration

^ swift_lint.swift:30:7: note: in declaration of 'Robot' class Robot: Machine { ^ swift_lint.swift:31:19: error: argument names for method 'move(direction:)' do not match those of overridden method 'move' override func move(direction: String) { ^ _ swift_lint.swift:40:51: warning: result of operator '+' is unused self.location.x - self.location.x + 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 Im a machine!")
  }
}

class Robot: Machine {
    override func move(direction: String) {
        switch(direction) {
            case "Up":
                self.location.y = self.location.y + 1
            case "Down":
                self.location.y = self.location.y - 1
            case "Left":
                self.location.x = self.location.x - 1
            case "Right":
                self.location.x - self.location.x + 1
            default:
                break
        }
    }

1 Answer

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

It is because your override function does not match the initial method, you need _ direction. Also your switch statement could be simplified

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":
                self.location.y -= 1
            case "Left":
                self.location.x -= 1
            case "Right":
                self.location.x += 1
            default:
                break
        }
    }

    }