有没有办法在 Dart 中定义可选参数“growable”？

Question

可选参数的默认值必须是常量。

class DirectoryTree {
  final Directory directory;
  final List<DirectoryTree> children;

  const DirectoryTree({
    required this.directory,
    this.children = List.empty(growable: true),
  });
}

有没有办法在 Dart 中定义可选参数“growable”？

Answer 1

你可以让孩子们像这样可选

class DirectoryTree {
  final Directory directory;
  final List<DirectoryTree> children;

  const DirectoryTree({
    required this.directory,
    List<DirectoryTree>? children,
  }) : children = children ?? const <DirectoryTree>[];