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

Niilo Pirttijärvi
Niilo Pirttijärvi
Courses Plus Student 2,354 Points

Enums and objects challenge?

I don't understand what the underscore does in this code. Could someone explain it's purpose?

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 .down:
            location.y -= 1
        case .up:
            location.y += 1

1 Answer

Gene Bogdanovich
Gene Bogdanovich
14,618 Points

In the "move" method, underscore allows you to omit parameter name "direction" when you call that method. If you were to call that method with underscore you'd write something like this: move(direction: .left) If you were to call that method without underscore you'd write something like this: move(.left)

It just reads better.