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wake_trait is now stable (#963)

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You probably know: `wake_trait` has been stable since 1.51.0 and no longer requires an attribute to enable
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Alexx Roche
2021-04-05 13:04:41 +02:00
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blog/content/edition-2/posts/12-async-await/index.md
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@@ -1643,7 +1643,7 @@ impl Wake for TaskWaker {
}
```
The trait is still unstable, so we have to add **`#![feature(wake_trait)]`** to the top of our `lib.rs` to use it. Since wakers are commonly shared between the executor and the asynchronous tasks, the trait methods require that the `Self` instance is wrapped in the [`Arc`] type, which implements reference-counted ownership. This means that we have to move our `TaskWaker` to an `Arc` in order to call them.
Since wakers are commonly shared between the executor and the asynchronous tasks, the trait methods require that the `Self` instance is wrapped in the [`Arc`] type, which implements reference-counted ownership. This means that we have to move our `TaskWaker` to an `Arc` in order to call them.
The difference between the `wake` and `wake_by_ref` methods is that the latter only requires a reference to the `Arc`, while the former takes ownership of the `Arc` and thus often requires an increase of the reference count. Not all types support waking by reference, so implementing the `wake_by_ref` method is optional, however it can lead to better performance because it avoids unnecessary reference count modifications. In our case, we can simply forward both trait methods to our `wake_task` function, which requires only a shared `&self` reference.