Aye, I thought I got it right, please help!

Question

test.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: .left) {
        // Enter your code below
        -> Point(x: x-1, y: y)
    }
}

Answer 1 · 2017-02-05T18:26:50Z

February 5, 2017 6:26pm

Hello Richard,

Yeah, this was a tricky one for me to figure out too. There are two ways(that I know of) that we can do this. First, we don’t want to change the function parameter type, we want to keep it as Direction. Only when calling the function would we use .left(or any of the other three cases of the Direction enum). Second, we want to switch on the internal variable(direction), which is of type Direction, and make our changes to location there, like so:

func move(_ direction: Direction) {
        // Enter your code below
        switch direction {
        case .left:
            location = Point(x: -1, y: 0)
        case .right:
            location = Point(x: 1, y: 0)
        case .up:
            location = Point(x: 0, y: 1)
        case .down:
            location = Point(x: 0, y: -1)

        }
    }

Of course we could say case Direction.left(and so on for the other cases), but we know that direction is of type Direction, so we can omit it. The shorter way to do it is just referencing the x and y properties of our location property and add or subtract 1, depending on the case, like so:

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

        }
    }

Both of those should work. I find these challenges a lot easier to figure out when doing them in an Xcode Playground first. Good ol’ code completion helps so much!

I hope I explained it well enough for you, and that it helps make it a bit easier to understand.

Dan

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Richard Pitts

Richard Pitts

Aye, I thought I got it right, please help!

1 Answer

Dan Lindsay

Dan Lindsay