onCancelled method

void Function() onCancelled(
  1. void callback()
)

Registers a callback to be called when this token is cancelled.

Returns a function that can be called to unregister the listener.

Implementation

void Function() onCancelled(void Function() callback) {
  if (_isCancelled) {
    callback();
    return () {};
  }

  _listeners.add(callback);
  return () => _listeners.remove(callback);
}