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

Posted by Ryan Breece
Ryan Breece
4,160 Points

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

Steve Hunter
Steve Hunter
57,712 Points

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.

Ryan Breece
Ryan Breece
4,160 Points

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

Ryan Breece
Ryan Breece
4,160 Points

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

Steve Hunter
Steve Hunter
57,712 Points

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.

Steve Hunter
Steve Hunter
57,712 Points 
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
}
i6ze5srftzgi8o5iu46z5etr
i6ze5srftzgi8o5iu46z5etr
6,931 Points

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 } } }

Bronson Barrett
Bronson Barrett
4,624 Points
Bronson Barrett
Bronson Barrett
4,624 Points

//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]

Steve Hunter
Steve Hunter
57,712 Points

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.

Ryan Breece
Ryan Breece
4,160 Points
Ryan Breece
Ryan Breece
4,160 Points

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.