when<TResult extends Object?> method

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

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