dart - 扩展运算符可以用于提供函数参数吗？

Question

我正在编写扩展 statelessWidget 的类，它的构建方法返回 Text()小部件。我需要将来自 Map<dynamic, dynamic> 中的构造函数的文本选项(对齐、阶梯等)传递给它.为什么我不能使用 spread像这样的运算符

final Map textOptions;
final String text;

build(BuildContext context) {
    return Text(text, ...textOptions)
}

Answer 1

您目前只能对集合文字使用展开运算符([] 用于 List，{} 用于 Map 或 Set).

来自 Bob Nystrom's article介绍 Dart 2.3 的新特性:

A spread can only appear in a place that can gracefully handle receiving zero or more values. Without completely overhauling the language’s execution model and turning it into Icon (which I find strangely appealing, but probably not practical…), there aren’t too many places that fit that constraint. Basically collection literals and maybe positional argument lists. (I wrote a proposal for the latter, but it’s quite complex so we aren’t doing it, at least not right now.)

但是，该提案并未完全涵盖您想要的内容，即将 Map 扩展到可选的命名参数中。