Rust version:
rustc 1.38.0-nightly (69656fa4c 2019-07-13)
打开async/await的future:
#![feature(async_await)]
#![feature(async_await)]
async fn get()->i32 {
println!("start");
std::thread::sleep(std::time::Duration::from_millis(1000));
1
}
async fn p() {
let n = get().await;
println!("n = {}", n);
}
fn main() {
let fut = p();
println!("called p");
futures::executor::block_on(fut);
}
定义了一个简单的get函数，返回1
p里面调用get并打印1
async和JavaScript的类似，返回的是future(js的是promise)，所以在Rust里面我们还需要一个executor来Run这个future，这里我们future用的版本是:
futures-preview = { version = "=0.3.0-alpha.17", features = ["compat"] }
主要原因就是async返回的是std::future::Future,而我们大部分三方库还是用的futures这个库，比如tokio，我们用tokio::run来试试会有个报错
--> src/main.rs:21:5
|
21 | tokio::run(fut);
| ^^^^^^^^^^ the trait `futures::future::Future` is not implemented for `impl std::future::Future`
|
= note: required by `tokio::runtime::threadpool::run`
error: aborting due to previous error
For more information about this error, try `rustc --explain E0277`.
error: Could not compile `async-await`.
To learn more, run the command again with --verbose.
tokio::run 是给 futures::future::Future,但是我们 async 的是 std::future::Future
现在最大的问题就是三方库还没有支持std future，所以如果要用就得compat一下
#![feature(async_await)]
use futures::compat::Future01CompatExt;
use futures::future::{FutureExt, TryFutureExt};
async fn get()->i32 {
println!("start");
std::thread::sleep(std::time::Duration::from_millis(1000));
1
}
async fn p() {
let n = get().await;
println!("n = {}", n);
}
fn main() {
let fut = p().unit_error().boxed().compat();
println!("called p");
tokio::run(fut);
}
Top comments (0)