Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

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

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

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
        }
    }

    }