飞镖和下划线 [英] Dart and underscores

问题描述

我决定在Dart中实现功能性underscore.js库。

我在'underscore.dart'中编写了函数，并显示了以下示例函数：

 库下划线； 
 
 List _filter（ff，List s）=>返回s..retainWhere（ff）; 
 
 List _dropWhile（ff，List s）=> s.skipWhile（ff）.toList（）; 
  

在我的主Dart程序中，然后添加了导入语句

  import'underscore.dart'; 
  

但是，我在未使用的导入这一行遇到了持续的错误，因此没有函数被识别。

进一步的测试表明，引起问题的是函数名上的下划线。

有什么想法吗？

解决方案

下划线表示该函数是图书馆私人的。也就是说，您不能在其他库中使用它。参见库和可见性。

库不仅提供API，而且是隐私单位：以下划线（_）开头的标识符仅在库内部可见。

I decided to implement the functional underscore.js library in Dart.

I wrote the functions in 'underscore.dart' with some example functions shown below:

library underscore;

List _filter (ff, List s) => return s..retainWhere(ff);

List _dropWhile(ff,List s) => s.skipWhile(ff).toList();

In my main Dart program, I then added the import statement

import 'underscore.dart';

However, I got the persistent error on that line of 'Unused Import', and so none of the functions were recognised.

It did work, though, when I redefined 'underscore.dart' as 'part of mainProg' and made 'mainProg' a library in its own right.

Further testing shows that it is the underscores on the function names that is causing the problem.

Any ideas?

解决方案

A prepending underscore means that the function is library private. That is, you can't use it in an other library. See Libraries and Visibility.

Libraries not only provide APIs, but are a unit of privacy: identifiers that start with an underscore (_) are visible only inside the library.

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