Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

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

tangtai chen
tangtai chen
4,844 Points
Posted by tangtai chen
tangtai chen
4,844 Points

Challenge Task 1 of Enumeration and Options, can someone help?

In the editor below you have two objects - classes named Point and Robot. The Robot stores its location as a point instance and contains a move function.

The task of this challenge is to complete the implementation for move. Move takes a parameter of type Direction which is an enumeration listing the possible movement directions.

When you tell the robot to move up (by specifying Direction.Up as the argument), the y coordinate should increase by 1. Similarly moving down means the y coordinate decreases by 1, moving right means the x coordinate increases by 1 and finally left means x decreases by 1.

here is my code it seems alright in Xcode but I could spot the mistake, can someone plz help!

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

3 Answers

Jeff McDivitt
Jeff McDivitt
23,970 Points
Jeff McDivitt
Jeff McDivitt
23,970 Points

It look as though you altered the code that was given in the challenge

You have

   func move(direction: Direction) {
        switch direction {
        case .up: location.y += 1
        case .down: location.y -= 1
        case .right: location.x += 1
        case .left: location.x -= 1
        }
    }
}

should be

//Do not remove the underscore in front of direction
   func move( _ direction: Direction) {
        switch direction {
        case .up: location.y += 1
        case .down: location.y -= 1
        case .right: location.x += 1
        case .left: location.x -= 1
        }
    }
}
tangtai chen
tangtai chen
4,844 Points
tangtai chen
tangtai chen
4,844 Points

thx it worked? what does the underscore do in the code anyways? in some challenges I removed the underscore of the code it worked

Jeff McDivitt
Jeff McDivitt
23,970 Points
Jeff McDivitt
Jeff McDivitt
23,970 Points

An underscore tells Swift that the parameter should have no label when called

Example 

func add( _ x: Int, _ y: Int {

}

When you call the function you will not need to include the labels x and y

let myAdd = add(1,2)