whenOrNull<TResult extends Object?> method

@optionalTypeArgs TResult? whenOrNull<TResult extends Object?>(TResult? $default(Map<int, Policy>? levels, SystemPolicy? system)?)

A variant of when that fallback to returning null

It is equivalent to doing:

switch (sealedClass) {
  case Subclass(:final field):
    return ...;
  case _:
    return null;
}

Implementation

@optionalTypeArgs
TResult? whenOrNull<TResult extends Object?>(
  TResult? Function(Map<int, Policy>? levels, SystemPolicy? system)? $default,
) {
  final _that = this;
  switch (_that) {
    case _PolicyConfig() when $default != null:
      return $default(_that.levels, _that.system);
    case _:
      return null;
  }
}