whenOrNull<TResult extends Object?> method

  1. @optionalTypeArgs
TResult? whenOrNull<TResult extends Object?>(
  1. TResult? $default(
    1. List<NameServerConfig>? servers,
    2. HostsWrapper? hosts,
    3. XrayAddress? clientIp,
    4. String? tag,
    5. DnsQueryStrategy? queryStrategy,
    6. bool? disableCache,
    7. bool? serveStale,
    8. int? serveExpiredTTL,
    9. bool? disableFallback,
    10. bool? disableFallbackIfMatch,
    11. bool? enableParallelQuery,
    12. bool? useSystemHosts,
    )?
)

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(
          List<NameServerConfig>? servers,
          HostsWrapper? hosts,
          XrayAddress? clientIp,
          String? tag,
          DnsQueryStrategy? queryStrategy,
          bool? disableCache,
          bool? serveStale,
          int? serveExpiredTTL,
          bool? disableFallback,
          bool? disableFallbackIfMatch,
          bool? enableParallelQuery,
          bool? useSystemHosts)?
      $default,
) {
  final _that = this;
  switch (_that) {
    case _DNSConfig() when $default != null:
      return $default(
          _that.servers,
          _that.hosts,
          _that.clientIp,
          _that.tag,
          _that.queryStrategy,
          _that.disableCache,
          _that.serveStale,
          _that.serveExpiredTTL,
          _that.disableFallback,
          _that.disableFallbackIfMatch,
          _that.enableParallelQuery,
          _that.useSystemHosts);
    case _:
      return null;
  }
}