Array<Dynamic> returns null on Android

Haxe
2 
//Works on Android but not Flash:
trace(array[0].get_x());

//Works on both:
trace(Reflect.getProperty(array[0], "x"));

//Works on both:
trace(cast(array[0], Sprite).x);

OpenFL has a getter and setter for the Sprite.x field. That means that there’s a get_x() and set_x() function, and you’re supposed to use those instead of accessing x directly.

So why can you use x normally? Shouldn’t it always fail?

Well, the Haxe compiler makes that replacement for you. When you type sprite.x, the compiler replaces it with sprite.get_x(). Since the get_x() function exists, everything works as expected.

The problem is, the compiler can’t tell if a Dynamic object is supposed to use a getter, so it assumes not. It won’t replace dynamic.x with dynamic.get_x(), and then at compile time, it tries to access x on an object that doesn’t have an x field. That’s why it returns null.

Here’s how the three solutions work:

  1. If you explicitly type out get_x(), then of course it will use that function. Problem is, that function doesn’t exist in Flash, so it won’t work in Flash.
  2. Reflect.getProperty() checks for a getter function. On Android, it’ll find a getter, and use that. On Flash, it won’t find a getter, so it’ll just use the x field. This is a bit slower, but it covers everything.
  3. If you tell the compiler that this will be a Sprite, then it will know about the getter, and it’ll replace x with get_x() on non-Flash targets. But the object has to be an actual Sprite, which kind of defeats the point.