when<TResult extends Object?> method

  1. @optionalTypeArgs
TResult when<TResult extends Object?>(
  1. TResult $default(
    1. Map<int, Policy>? levels,
    2. SystemPolicy? system
    )
)

A switch-like method, using callbacks.

As opposed to map, this offers destructuring. It is equivalent to doing:

switch (sealedClass) {
  case Subclass(:final field):
    return ...;
  case Subclass2(:final field2):
    return ...;
}

Implementation

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