rust - 我怎样才能延长结构的生命周期，以便我可以用它调用 tokio::run？

Question

我有一个有效的函数:

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()));
}

playground

在这种情况下，我想创建一个包含一些参数(label)的结构，方法 run 将利用这些参数:

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());
}

playground

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 活得不够长？
我在尝试调用 ir.run() 的同一范围内创建了它，因此我认为它会一直存在。

Answer 1

如果你重写:

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...

自 tokio::run Future 需要一个'static 生命周期:

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 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))
}