attachOneShot method
Attaches a function that will be executed when notify() is called. The listener is detached automatically on notify(), which invalidates the listener key after first invocation.
Returns a key object that can be used to detach the listener from the notifier to stop execution on notify() call and avoid memory leaks.
Implementation
Object attachOneShot(Function listener) {
final key = attach(listener);
_oneShotKeys.add(key);
return key;
}