prefer_is_empty

Use isEmpty for Iterables and Maps.

此规则自 Dart 2.0 版本起可用。

_规则集：core , recommended , flutter _

此规则提供 快速修复 。

DON'T use length to see if a collection is empty.

The Iterable contract does not require that a collection know its length or be able to provide it in constant time. Calling length just to see if the collection contains anything can be painfully slow.

Instead, there are faster and more readable getters: isEmpty and isNotEmpty. Use the one that doesn't require you to negate the result.

BAD:

if (lunchBox.length == 0) return 'so hungry...';
if (words.length != 0) return words.join(' ');

GOOD:

if (lunchBox.isEmpty) return 'so hungry...';
if (words.isNotEmpty) return words.join(' ');

要启用 prefer_is_empty 规则，请在你的 analysis_options.yaml 文件中，在 linter > rules 下添加 prefer_is_empty ：

linter:
  rules:
    - prefer_is_empty

除非另有说明，否则本网站上的文档反映的是 Dart 3.6.0。页面最后更新于 2025-02-05。 查看源代码 或 报告问题.