Rust-async/await用法

1、异步

如下代码：先打印hhh，再打印my_function中的log。

#[tokio::main]
async fn main() {
    let f = my_function();
    println!("hhhhh");
    f.await;
}

async fn my_function() {
    println!("i am a async function");
    let s1 = read_from_database().await;
    println!("first result:{s1}");
    let s2 = read_from_database().await;
    println!("second result:{s2}");
}

async fn read_from_database() -> String {
    "DB Result".to_owned()
}

最外层调用Future需要手动调用，所以用到了第三方库tokio，不然会报错main方法不能加async。三方库的作用是构建一个运行时并调用main方法。

/tokio = { version = "1.24.2", features = ["full"] }

2、并发

use std::time::Duration;
use tokio::time::sleep;

#[tokio::main]
//#[tokio::main(flavor = "current_thread")]会强制tokio多任务都在一个线程-主线程
async fn main() {
    let mut handles = vec![];
    for i in 0..2 {
        let handle = tokio::spawn(async move {
            my_function(i).await;
        });
        handles.push(handle);
    }

    for handle in handles {
        handle.await.unwrap();
    }
}

async fn my_function(i: i32) {
    println!("i am a async function");
    let s1 = read_from_database().await;
    println!("[{i}] first result:{s1}");
    let s2 = read_from_database().await;
    println!("[{i}] second result:{s2}");
}

async fn read_from_database() -> String {
    sleep(Duration::from_millis(50)).await; //此处await缺失会变同步
    "DB Result".to_owned()
}

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