addObserver static method

void Function() addObserver(
  1. JObserverDelegate observer
)

Registers observer and returns a function that removes it.

Registering the same instance twice has no effect; the returned function is idempotent.

Implementation

static void Function() addObserver(JObserverDelegate observer) {
  if (!_delegates.any((registered) => identical(registered, observer))) {
    _delegates.add(observer);
  }
  return () => removeObserver(observer);
}