Issue with task of "Swift Recap Part 2" code challenge in "Build a Simple iPhone App with Swift 2.0"

Hello, I'm not sure what's the problem with my codes, cause I just learned the oriented object last week. Please help me to figure it out. Thanks a lot!

In the editor you've been provided with two classes - Point to represent a coordinate point and Machine. The machine has a move method that doesn't do anything because most machines are motionless.

Your task is to subclass Machine and create a new class named Robot. In the Robot class, override the move method and provide the following implementation. If you enter the string "Up" the y coordinate of the Robot's location increases by 1. "Down" decreases it by 1. If you enter "Left", the x coordinate of the location property decreases by 1 while "Right" increases it by 1.

Note: If you use a switch statement you can use the break statement in the default clause to exit the current iteration.

```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! I'm a machine!")

}

}

// Enter your code below

var enter: String = "none"

class Robot: Machine {

override func move(direction: String) {
    func move(enter: String) -> Point {
    switch enter {
    case "Up":
        location = Point(x: 0, y: 1)
        return location
    case "Down":
        location = Point(x: 0, y: -1)
        return location
    case "Left":
        location = Point(x: -1, y: 0)
        return location
    case "Right":
        location = Point(x: 1, y: 0)
        return location

    default:
        print("dont move")

} } } }

enter = "Up"```