5.10 Local static variables

since Haxe 4.3.0

static var and static final declarations within a function create variables that are scoped to the function (they cannot be referred to from outside the function), but are only initialized once.

This can be used to implement a cache or memoization pattern for functions without creating too many class fields.

class Main {
  static function getData() {
    static var cache:Null<String> = null;
    if (cache == null) {
      cache = slowOperation();
    return cache;

  static function slowOperation() {
    trace("performing slow operation...");
    return "result";

  static public function main() {
    trace(getData()); // performing slow operation... result
    trace(getData()); // result

Similarly to static class variables, the initial value assigned to a local static variable (if any) must not refer to instance variables or arguments of the current function.