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iOS Build a Simple iPhone App with Swift 2.0 Getting Started with iOS Development Swift Recap Part 2

Subclass Question. The code runs. What am I missing?

I added what they are asking for. The code seems to be running as I can see the new value change when I create an Instance of move"up". Am I missing something?

In the editor you've been provided with two classes - Point to represent a coordinate point and Machine. The machine has a move method that doesn't do anything because most machines are motionless. Your task is to subclass Machine and create a new class named Robot. In the Robot class, override the move method and provide the following implementation. If you enter the string "Up" the y coordinate of the Robot's location increases by 1. "Down" decreases it by 1. If you enter "Left", the x coordinate of the location property decreases by 1 while "Right" increases it by 1. Note: If you use a switch statement you can use the break statement in the default clause to exit the current iteration.

classes.swift
class Point {
    var x: Int
    var y: Int

    init(x: Int, y: Int){
        self.x = x
        self.y = y
    }
}


class Machine {
    var location: Point

    init() {
        self.location = Point(x: 0, y: 0)
    }

    func move(direction: String) {
        print("Do nothing! I'm a machine!")
    }
}

// Enter your code below

class Robot: Machine {


    override init() {
        super.init()

    }

    override func move(direction: String) {
        switch direction{
            case "Up" : location.y + 1
            case "Down" : location.y - 1
            case "Left" : location.x - 1
            case "Right" : location.x + 1
        default : break
        }
    }
}


let player = Robot()
player.location = Point(x: 2, y: 2)
player.move("Up")

print(player.location.y)

3 Answers

Hi Ryan,

You've done the hard bit here! But, your increment and decrement execution isn't quite right. You're not assigning the values back into the x or y components. You can do that long-hand, or just use the ++ or -- operators. And you don't need to mess with the init method. It should look something like:

class Robot: Machine {
  override func move(direction: String){
        switch direction{
            case "Up" : location.y++
            case "Down" : location.y--
            case "Left" : location.x--
            case "Right" : location.x++
            default : break
        }
  }
}

I hope that helps.

Steve.

Thank you for the quick response. I have been reading and watching youtube videos for a while on this.

For Learning, would you mind showing me the long hand version of making this happen.

No problem!

Saying location.y + 1 doesn't affect location.y. You need to assign something back into it. Going long would look like location.y = location.y + 1. Using the increment operator works just the same.

Steve.

switch direction{
  case "Up" : location.y = location.y + 1
  case "Down" : location.y = location.y - 1
  case "Left" : location.x = location.x - 1
  case "Right" : location.x = location.x + 1
  default : break
}

class Robot: Machine { override func move(_ direction: String) { switch direction { case "Up": location.y += 1 case "Down": location.y -= 1 case "Left": location.x -= 1 case "Right": location.x += 1 default: break } } }

//There seems to be an error in the initial template code already added by Team Treehouse.

class Point {
    var x: Int
    var y: Int

    init(x: Int, y: Int){
        self.x = x
        self.y = y
    }
}


class Machine {
    var location: Point

    init() {
        self.location = Point(x: 0, y: 0)
    }

    func move(direction: String) {
        print("Do nothing! Im a machine!") /*I deleted the apostrophe in Im (I'm), and my code compiled... Don't know if anyone had this issue, but it wouldn't let me complete the challenge until I made this change. */
    }
}

// Enter your code below

class Robot: Machine {


    override init() {
        super.init()

    }

//an alternative way to increase and decrease the x,y values is with the += and -=

    override func move(direction: String) {
        switch direction{
            case "Up" : location.y += 1
            case "Down" : location.y -= 1
            case "Left" : location.x -= 1
            case "Right" : location.x += 1
        default : break
        }
    }
}

[MOD: edited code blocks. SH]

Hi Bronson,

Deleting the apostrophe will make the code format in colours. Alternatively, you can escape the apostrophe character with a backslash - your code will pass the challenge either way. Deleting the apostrophe did not make your code pass; it just made the colour format appear.

Steve.

Yes, makes sense. I was thinking to myself, "How is this returning?" But I because I am new to this still, I started trying to find solutions in the init or the method return. Thank you alot.