rust - 如何延长结构的生命周期,以便可以使用它调用 tokio::run?
问题描述
我有一个有效的功能:
extern crate tokio;
use std::time::{Duration, Instant};
use tokio::prelude::*;
use tokio::timer::Interval;
fn run(label: String) -> impl Future<Item = (), Error = ()> {
Interval::new(Instant::now(), Duration::from_millis(1000))
.for_each(move |instant| {
println!("fire; instant={:?}, label={:?}", instant, label);
Ok(())
})
.map_err(|e| panic!("interval errored; err={:?}", e))
}
fn main() {
tokio::run(run("Hello".to_string()));
}
我想创建一个结构,label
在这种情况下,它可以保存一些参数(),并使用一个run
可以利用参数的方法:
extern crate tokio;
use std::time::{Duration, Instant};
use tokio::prelude::*;
use tokio::timer::Interval;
struct Ir {
label: String,
}
impl Ir {
fn new(label: String) -> Ir {
Ir { label }
}
fn run(&self) -> impl Future<Item = (), Error = ()> + '_ {
Interval::new(Instant::now(), Duration::from_millis(1000))
.for_each(move |instant| {
println!("fire; instant={:?}, label={:?}", instant, self.label);
Ok(())
})
.map_err(|e| panic!("interval errored; err={:?}", e))
}
}
fn main() {
let ir = Ir::new("Hello".to_string());
tokio::run(ir.run());
}
我得到的是:
error[E0597]: `ir` does not live long enough
--> src/main.rs:28:16
|
28 | tokio::run(ir.run());
| ^^ borrowed value does not live long enough
29 | }
| - borrowed value only lives until here
|
= note: borrowed value must be valid for the static lifetime...
我已经阅读了“Rust by Example”中的“Advanced Lifetimes”和“Validating References with Lifetimes”,但我仍然不明白如何修复它。
为什么ir
活的不够长?
我已经在我试图调用的同一范围内创建了它ir.run()
,所以我认为它会一直存在。
解决方案
如果重写:
tokio::run(ir.run());
作为:
tokio::run(Ir::run(&ir))
错误变得更清楚了:
error[E0597]: `ir` does not live long enough
--> src/main.rs:28:24
|
28 | tokio::run(Ir::run(&ir));
| ^^ borrowed value does not live long enough
29 | }
| - borrowed value only lives until here
|
= note: borrowed value must be valid for the static lifetime...
因为未来tokio::run
需要一生:'static
pub fn run<F>(future: F)
where
F: Future<Item = (), Error = ()> + Send + 'static,
为避免生命周期问题,请考虑使用该Ir
值:
fn run(self) -> impl Future<Item = (), Error = ()> {
Interval::new(Instant::now(), Duration::from_millis(1000))
.for_each(move |instant| {
println!("fire; instant={:?}, label={:?}", instant, self.label);
Ok(())
})
.map_err(|e| panic!("interval errored; err={:?}", e))
}