@ -4,11 +4,11 @@ Rust has two kinds of types commonly referred to as `Future`:
- the first is `std::future::Future` from Rust’s [standard library](https://doc.rust-lang.org/std/future/trait.Future.html).
- the second is `futures::future::Future` from the [futures-rs crate](https://docs.rs/futures-preview/0.3.0-alpha.17/futures/prelude/trait.Future.html), currently released as `futures-preview`.
- the second is `futures::future::Future` from the [futures-rs crate](https://docs.rs/futures/0.3/futures/prelude/trait.Future.html).
The future defined in the [futures-rs](https://docs.rs/futures-preview/0.3.0-alpha.17/futures/prelude/trait.Future.html) crate was the original implementation of the type. To enable the `async/await` syntax, the core Future trait was moved into Rust’s standard library and became `std::future::Future`. In some sense, the `std::future::Future` can be seen as a minimal subset of `futures::future::Future`.
The future defined in the [futures-rs](https://docs.rs/futures/0.3/futures/prelude/trait.Future.html) crate was the original implementation of the type. To enable the `async/await` syntax, the core Future trait was moved into Rust’s standard library and became `std::future::Future`. In some sense, the `std::future::Future` can be seen as a minimal subset of `futures::future::Future`.
It is critical to understand the difference between `std::future::Future` and `futures::future::Future`, and the approach that `async-std` takes towards them. In itself, `std::future::Future` is not something you want to interact with as a user—except by calling `.await` on it. The inner workings of `std::future::Future` are mostly of interest to people implementing `Future`. Make no mistake—this is very useful! Most of the functionality that used to be defined on `Future` itself has been moved to an extension trait called [`FuturesExt`](https://docs.rs/futures-preview/0.3.0-alpha.17/futures/future/trait.FutureExt.html). From this information, you might be able to infer that the `futures` library serves as an extension to the core Rust async features.
It is critical to understand the difference between `std::future::Future` and `futures::future::Future`, and the approach that `async-std` takes towards them. In itself, `std::future::Future` is not something you want to interact with as a user—except by calling `.await` on it. The inner workings of `std::future::Future` are mostly of interest to people implementing `Future`. Make no mistake—this is very useful! Most of the functionality that used to be defined on `Future` itself has been moved to an extension trait called [`FuturesExt`](https://docs.rs/futures/0.3/futures/future/trait.FutureExt.html). From this information, you might be able to infer that the `futures` library serves as an extension to the core Rust async features.
In the same tradition as `futures`, `async-std` re-exports the core `std::future::Future` type. You can actively opt into the extensions provided by the `futures-preview` crate by adding it to your `Cargo.toml` and importing `FuturesExt`.
yjhmelody
5 years ago