when<TResult extends Object?> method

@optionalTypeArgs TResult when<TResult extends Object?>(TResult $default(String? url, String label, bool active))

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(String? url, String label, bool active) $default,
) {
  final _that = this;
  switch (_that) {
    case _IsibookReservationLink():
      return $default(_that.url, _that.label, _that.active);
  }
}