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

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

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

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

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)