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iOS Swift 2.0 Enumerations and Optionals Introduction to Enumerations Enums and Objects

Posted by Matt Conway
Matt Conway
1,572 Points

Enumerations & Optionals

Wonder why this doesn't work?

classes.swift 
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
        let Direction.Up = y+1
        let Direction.Down = y-1
        let Direction.Right = x+1
        let Direction.Left = x-1
    }
}

1 Answer

jcorum
jcorum
71,830 Points
jcorum
jcorum
71,830 Points

Matt, here's what you want the function to look like:

    func move(direction: Direction) {
        // Enter your code below
        if direction == .Up {
          location.y++
        } else if direction == .Down {
          location.y--
        } else if direction == .Right {
          location.x++
        } else {
          location.x--
        }
    }

First, there's no need to create constants inside the function. So no let keywords.

Second, the shorthand way to write x = x + 1 is x++, not x+1

Third, you only want the robot direction to change in one way, not four ways, when the method is called. So you will need a switch statement or an if...else if...else... statement. I show you the latter in the above code.

Fourth, direction is an Direction object, so it's going to have one of four values: .Up, .Down, .Right or .Left. You will test to see which in each path of the switch or if/else.

Hope this helps.