(tokio::spawn) 借来的值存在的时间不够长——参数要求借用 `sleepy` 用于 `'static` [英] (tokio::spawn) borrowed value does not live long enough -- argument requires that `sleepy` is borrowed for `'static`
问题描述
这个 MWE 展示了 tokio::spawn
在 for in
循环中的使用.注释代码 sleepy_futures.push(sleepy.sleep_n(2));
工作正常,但不运行/轮询异步函数.
This MWE shows the use of tokio::spawn
in for in
loop. The commented code sleepy_futures.push(sleepy.sleep_n(2));
works fine, but does not run/poll the async function.
基本上,我想同时运行一堆异步函数.我很高兴更改 Sleepy
的实现或使用其他库/技术.
Basically, I would like to run a bunch of async functions at the same time. I am happy to change the implementation of Sleepy
or use another library/technique.
pub struct Sleepy;
impl Sleepy {
pub async fn sleep_n(self: &Self, n: u64) -> String {
sleep(Duration::from_secs(n));
"test".to_string()
}
}
#[tokio::main(core_threads = 4)]
async fn main() {
let sleepy = Sleepy{};
let mut sleepy_futures = vec::Vec::new();
for _ in 0..5 {
// sleepy_futures.push(sleepy.sleep_n(2));
sleepy_futures.push(tokio::task::spawn(sleepy.sleep_n(2)));
}
let results = futures::future::join_all(sleepy_futures).await;
for result in results {
println!("{}", result.unwrap())
}
}
推荐答案
这是一个粗略的修复方法:
Here's a rough stab at fixing it:
use tokio::time::delay_for;
pub struct Sleepy;
impl Sleepy {
pub async fn sleep_n(n: u64) -> String {
delay_for(Duration::from_secs(n)).await;
"test".to_string()
}
}
现在它不再锚定到任何特定的 Sleepy 实例,消除了生命周期问题.你可以像 Sleepy::sleep_n
一样称呼它.
Where now it's no longer anchored to any particular Sleepy instance, eliminating the lifetime issue. You'd call it like Sleepy::sleep_n
.
如果需要 &self
则需要更多的工作:
It takes a little more work if that &self
is required:
use std::sync::Arc;
use std::time::Duration;
use std::vec;
use tokio;
use tokio::time::delay_for;
pub struct Sleepy;
impl Sleepy {
pub async fn sleep_n(&self, n: u64) -> String {
// Call .await here to delay properly
delay_for(Duration::from_secs(n)).await;
"test".to_string()
}
}
#[tokio::main(core_threads = 4)]
async fn main() {
env_logger::init();
let sleepy = Arc::new(Sleepy {});
let mut sleepy_futures = vec::Vec::new();
for _ in 0..5 {
let sleepy = sleepy.clone();
// Dictate that values are moved into the task instead of
// being borrowed and dropped.
sleepy_futures.push(tokio::task::spawn(async move {
sleepy.sleep_n(2).await
}));
}
let results = futures::future::join_all(sleepy_futures).await;
for result in results {
println!("{}", result.unwrap())
}
}
这里用Arc
来包裹对象,因为task
可能会用到线程,所以Rc
是不够的.
Here Arc
is used to wrap the object since task
may use threads, so Rc
isn't sufficient.
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