Here’s a neat trick I discovered today while working on Iridescence.

Haxe has native macros that are very different from those found in C; rather than using a separate pre-processing language, Haxe macros are simply snippets of Haxe code that are run at compile time instead of run time.

In native builds, Iridescence populates its soundtrack dynamically by searching for all song files in the /assets/music folder. On more restrictive platforms like Flash, all assets have to be known at compile time so they can be embedded in the SWF, which meant I needed to create a list of files manually and update it whenever I added a new song. I wrote this little macro to iterate through the music folder at compile time and build a list of song files automatically.

macro public static function getSongList(extension:String)
{
	var songs = FileSystem.readDirectory("assets/music")
		.filter(function(s) return s.endsWith(extension))
		.map(function(s) return "assets/music/" + s)
		.array();

	return Context.makeExpr(songs, Context.currentPos());
}