whenOrNull<TResult extends Object?> method

@optionalTypeArgs TResult? whenOrNull<TResult extends Object?>({ TResult? network(String url, ImageParams params)?, TResult? base64(String base64Code, ImageParams params)?, TResult? filePath(String filePath, ImageParams params)?, TResult? asset(String assetPath, ImageParams params)?, })

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(String url, ImageParams params)? network,
  TResult? Function(String base64Code, ImageParams params)? base64,
  TResult? Function(String filePath, ImageParams params)? filePath,
  TResult? Function(String assetPath, ImageParams params)? asset,
}) {
  final _that = this;
  switch (_that) {
    case MyNetworkImage() when network != null:
      return network(_that.url, _that.params);
    case MyBase64Image() when base64 != null:
      return base64(_that.base64Code, _that.params);
    case MyFilePathImage() when filePath != null:
      return filePath(_that.filePath, _that.params);
    case MyAssetImage() when asset != null:
      return asset(_that.assetPath, _that.params);
    case _:
      return null;
  }
}