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

Posted by hillionaire
hillionaire
22,539 Points

HOW?

how

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: Direction) {
        // Enter your code below
        switch(direction) {
        case Direction.Up: location.y += 1

        case Direction.Down: location.y -= 1

        case Direction.Left: location.x -= 1

        case Direction.Right: location.x += 1

            }
        }
    }
}

4 Answers

akyya mayberry
akyya mayberry
3,668 Points
akyya mayberry
akyya mayberry
3,668 Points

I can't retrieve my old code. But I do not recall the move method initially not requiring external arg name (the underscore). I copied hillionaire's code. I removed the extra parenthesis in his code, added the underscore in the move definition to remove the external name, lowercased the member names in the method body and the rest of his/her code passed as is. Weird.

Daniel Santos
Daniel Santos
34,969 Points

That is weird.

Daniel Santos
Daniel Santos
34,969 Points
Daniel Santos
Daniel Santos
34,969 Points

The problem is in the case of the switch statement. The cases in the enum Direction are lower case. You are writing it upper case. You are probably getting an undefined error. Here is another way of doing it, remember Swift is a pretty smart language, in my opinion.

switch direction {
          case .left: location.x -= 1
          case .right: location.x += 1
          case .up: location.y += 1
          case .down: location.y -= 1
}

Because Swift knows the type of direction, explicitly writing the type is not necessary.

Hope this helped.

-Dan

akyya mayberry
akyya mayberry
3,668 Points
akyya mayberry
akyya mayberry
3,668 Points

Daniel Santos it doesn't work! Must be some kind of bug on Treehouse end. For one the directions is wrong by telling us to refer to it as Direction.Up which is hillinair may have done it that way. After I kept getting compiler errors, I tried it that way as well. Also, your .down is missing an assignment.

akyya mayberry
akyya mayberry
3,668 Points
akyya mayberry
akyya mayberry
3,668 Points

I found the other issue. Once you follow Daniels feedback to adjust your switch statement, you also have to make changes to your enum. The problem is how they want us to define the cases in our enum. They are forcing us to use the alternate syntax that was introduced in the video. The syntax where the case statements all are defined together

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

Daniel Santos
Daniel Santos
34,969 Points

That is very strange, my code worked fine with the enum provided by the challenge. Here is my full solution:

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 .left: location.x -= 1
          case .right: location.x += 1
          case .up: location.y += 1
          case .down: location.y -= 1
        }   
    }
}