Static Extension

Static extensions provide a mechanism to "extend" existing types with new functionality without modifying their original source code. This can be used either with real and custom classes.

Here is a basic Static Extension example:

using StringTools;

class IntExtender {
  static public function triple(i:Int) {
    return i * 3;
  }
}

// need to create/import the custom class
// before setting the extension (limitation for now)
using IntExtender;

var str = "  Hello World!  ";

function create() {
  trace(str.trim()); // "Hello World!"
  trace(12.triple()); // 36
}

More information about static extension here.