doesn't add or subtract the value when calling the function move

So I was doing the code challenge to learn more about enums and I figured out the solution to the problem I'm pretty sure(i haven't checked it yet). but basically I went to test it out in the swift playgrounds and it does not add a value or subtract a value when you call the move function. hopefully my code will better explain it, but basically if i do move(.left) and check the x value of Robot's point after words it is still zero, Im guessing this has something to do with reference types and also class Robot initializes point with hardcoded values. Idk maybe im going somewhere with that idea here is my code oh and i guess it won't let me upload my playground so ill type out what im doing

//new instance of robot let newRobot = Robot() newRobot.location // should return 0,0 if you print() it newRobot.move(.left) // changes the value of locations x from 0 to -1 newRobot.location //should return the new changes of x but still says 0,0

class Point {
    var x: Int
    var y: Int

    init(x: Int, y: Int) {
        self.x = x
        self.y = y
    }
}

enum Direction {
    case left
    case right
    case up
    case down
}

class Robot {
    var location: Point

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

    func move(_ direction: Direction) {
        // Enter your code below
        switch direction {
          case .up: self.location.y + 1
          case .left: self.location.x - 1
          case .right: self.location.x + 1
          case .down: self.location.y - 1
        }
    }
}