Using Map with Point as Key

Help
#1

Hi,

I want to associate Bitmaps with Points, so I thought that using a Map<Point, Bitmap> would be a good idea, but how do I use it after setting it?

Here’s what I did:

myMap.set(new Point(bitmap.x, bitmap.y), bitmap);

After that, what am I suppose to write to get a bitmap from a specific coordinate?

myMap.get(PLEASE_HELP_ME);

Thank you! :slight_smile:

#2

You could use Map<Point, BitmapData>, but then it will be based on the Point instance, not the coordinates, so you would have to keep track of your Point objects to look up your images.

The ideal might be if you can use Int-based coordinates, perhaps you could use Map<Int, Map<Int, BitmapData>>, like

var map = new Map<Int, Map<Int, BitmapData>> ();
if (!map.exists (x)) map.set (x, new Map ());
map[x][y] = bitmapData;

You can use Float as a key value in a Dictionary, but the risk with Float values is that two numbers that are supposed to be the same could end up not matching due to minor little differences, or you could end up with so many key values that it bloats the data structure too much

#3

Thank you for your reply!

I think it would work, but then, how can I access all bitmaps in a for loop? At first, I was doing this:

for (bitmap in myMap) {
	...
}

But now, doing so will only get me to the Map inside the Map. How should I proceed?

Thank you for all the help!

#4

You could do

var childMap;

for (x in map.keys ()) {
    
    childMap = map[x];
    
    for (y in childMap.keys ()) {
        trace (x, y, childMap[y[);
    }
}

…if you need the x and y values, in addition to the BitmapData, otherwise, something like this would work if you only need the BitmapData

for (childMap in map) {
    for (bitmapData in childMap) {
        trace (bitmapData);
    }
}

However, iterating over a Map like this generates a new Array every time you do it. As a result, I would strongly recommend that you use an Array, List or other data structure designed for iteration if you have to do it regularly. For example:

private var images:Array<BitmapData>;
private var imageByPosition:Map<Int, Map<Int, BitmapData>>;

On that note, you could use an Array for this instead of Map if you want :slight_smile:

var images = new Array<Array<BitmapData>> ();
if (images[x] == null) images[x] = new Array ();
images[x][y] = bitmapData;

I think this would work, the question would be what value you get if you reference an index that has not been used yet