forEach method Null safety

void forEach(
  1. void f(
    1. String key,
    2. String value

Applies action to each key/value pair of the map.

Calling action must not add or remove keys from the map.


void forEach(void f(String key, String value)) {
  for (var i = 0; true; i++) {
    final key = _key(i);
    if (key == null) return;

    f(key, this[key]!);