BSP Dungeon Generator giving an unfixable error - ios

Question

I'm working on translating this ActionScript tutorial on binary space partitioning into Swift so I can use it in my rogue-like game. I came across a hitch.
In the article, the writer initializes his class like so:
public function Leaf(X:int, Y:int, Width:int, Height:int)
{
// initialize our leaf
x = X;
y = Y;
width = Width;
height = Height;
}
When I translated this into Swift, I ran into an error. The code above doesn't initialize all its declared values. This leads me into an impossible error that I can't seem to fix. Somehow, the writer of the article initializes his leftChild and rightChild variables with this function that is outside the initialization scope.
public function split():Boolean
{
// begin splitting the leaf into two children
if (leftChild != null || rightChild != null)
return false; // we're already split! Abort!
// determine direction of split
// if the width is >25% larger than height, we split vertically
// if the height is >25% larger than the width, we split horizontally
// otherwise we split randomly
var splitH:Boolean = FlxG.random() > 0.5;
if (width > height && width / height >= 1.25)
splitH = false;
else if (height > width && height / width >= 1.25)
splitH = true;
var max:int = (splitH ? height : width) - MIN_LEAF_SIZE; // determine the maximum height or width
if (max <= MIN_LEAF_SIZE)
return false; // the area is too small to split any more...
var split:int = Registry.randomNumber(MIN_LEAF_SIZE, max); // determine where we're going to split
// create our left and right children based on the direction of the split
if (splitH)
{
leftChild = new Leaf(x, y, width, split);
rightChild = new Leaf(x, y + split, width, height - split);
}
else
{
leftChild = new Leaf(x, y, split, height);
rightChild = new Leaf(x + split, y, width - split, height);
}
return true; // split successful!
}
Which is somehow ok in ActionScript, but in Swift it leads me to my problem.
Here is my translated code (Swift):
private let mapWidth:Int = 50
private let mapHeight:Int = 50
class Leaf {
var leftLeaf = [Leaf]()
var rightLeaf = [Leaf]()
var minLeafSize:Int = 6
var x, y, width, height: Int
var leftChild:Leaf
var rightChild:Leaf
init (X:Int, Y:Int, W:Int, H:Int) {
x = Y
y = Y
width = W
height = H
let maxLeafSize:UInt = 20
var leaves = [Leaf]()
// first, create a Leaf to be the 'root' of all Leafs.
let root = Leaf(X: 0, Y: 0, W: mapWidth, H: mapHeight)
leaves.append(root)
var didSplit:Bool = true
// we loop through every Leaf in our Vector over and over again, until no more Leafs can be split.
while (didSplit) {
didSplit = false
for l in leaves {
if l.leftLeaf.isEmpty == true && l.rightLeaf.isEmpty == true {
// if this Leaf is too big, or 75% chance...
if l.width > maxLeafSize || l.height > maxLeafSize || Int(arc4random_uniform(100)) > 25 {
if (l.split()) {
// if we did split, push the child leafs to the Vector so we can loop into them next
leaves.append(l.leftChild)
leaves.append(l.rightChild)
didSplit = true
}
}
}
}
}
}
func split() -> Bool {
if leftLeaf.isEmpty == true || rightLeaf.isEmpty == true {
return false
}
var splitH = arc4random_uniform(100) > 50 ? true : false
if width > height && Double(width / height) >= 1.25 {
splitH = false
}
if height > width && Double(height / width) >= 1.25 {
splitH = true
}
let max:Int = (splitH ? height : width) - minLeafSize // determine the maximum height or width
if max <= minLeafSize { return false }
let split:Int = Int(arc4random_uniform(UInt32(minLeafSize - max) + UInt32(max)))
if (splitH) {
leftChild = Leaf(X: x, Y: y, W: width, H: split)
rightChild = Leaf(X: x, Y: y + split, W: width, H: height - split)
leftLeaf.append(leftChild)
rightLeaf.append(rightChild)
} else {
leftChild = Leaf(X: x, Y: y, W: split, H: height)
rightChild = Leaf(X: x + split, Y: y, W: width - split, H: height);
leftLeaf.append(leftChild)
rightLeaf.append(rightChild)
}
return true
}
}
It is identical (as far as I can figure) to the ActionScript code in the article. But it is giving me an error. The leftChild and rightChild variables aren't initialized in my init method. When I move the split() -> Bool function into the init method it won't let me use the function, giving me an error "Value of type Leaf has no member split()". Removing the l from the if (l.spit()) line gives me a second error "Use of local variable 'split' before its declaration". The split() function has to be outside the initialization scope.
If I attempt to initialize leftChild and rightChild like so:
init (X:Int, Y:Int, W:Int, H:Int) {
x = Y
y = Y
width = W
height = H
leftChild = Leaf(X: x, Y: y, W: width, H: height)
rightChild = Leaf(X: x, Y: y, W: width, H: height)
}
It creates an infinite loop that eventually causes a crash.
The code should be initializing leftChild and rightChild in the split() -> Bool function but I don't think that's how it works in Swift. You should be able to copy/paste it into a Swift file and get the same errors.
Why is this happening? Is my code poorly written? How can I fix this?

Answer 1

In ActionScript, uninitialised variables are automatically evaluated with the special value undefined; also, in ActionScript, undefined == null, which is why if (leftChild != null || rightChild != null) works.
In Swift, you need to explicitly allow your variables to be nilable. The variables you are worried about need to start off as nil (which they automatically will, if you allow them to, by setting their type to Optional - note the question mark):
var leftChild:Leaf?
var rightChild:Leaf?