异步特征

Async methods in traits are were stabilized only recently, in the 1.75 release. This required support for using return-position impl Trait (RPIT) in traits, as the desugaring for async fn includes -> impl Future<Output = ...>.

However, even with the native support today there are some pitfalls around async fn and RPIT in traits:

  • Return-position impl Trait captures all in-scope lifetimes (so some patterns of borrowing cannot be expressed)

  • Traits whose methods use return-position impl trait or async are not dyn compatible.

If we do need dyn support, the crate async_trait provides a workaround through a macro, with some caveats:

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Speaker Notes

  • async_trait 易于使用，但请注意，它通过堆分配来实现这一点。这种堆分配会产生性能开销。

  • 对于 async trait 的语言支持中的挑战是深入 Rust的，并且可能不值得深入描述。如果您对深入了解感兴趣，Niko Matsakis 在这篇文章中对它们做了很好的解释。

  • 尝试创建一个新的 sleeper 结构，使其随机休眠一段时间，并将其添加到 Vec 中。