whenOrNull<TResult extends Object?> method

  1. @optionalTypeArgs
TResult? whenOrNull<TResult extends Object?>({
  1. TResult? file(
    1. File file
    )?,
  2. TResult? network(
    1. String url
    )?,
})

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(File file)? file,
  TResult? Function(String url)? network,
}) {
  final _that = this;
  switch (_that) {
    case XXFile() when file != null:
      return file(_that.file);
    case XXImage() when network != null:
      return network(_that.url);
    case _:
      return null;
  }
}