tokio::fs::File::open(path: T + 'static)
需要其参数的'static
生命周期。path
这是有道理的,因为它是在程序执行期间在运行时线程中处理的。我认为如果你可以通过自己的生命周期会更有意义,因为运行时不需要一直运行,所以你可以扔掉一些东西。我理解错了吗?
我现在想留下来'static
,所以我的问题是......
我有一个trait TraitN
和一些struct StructX { path: String, }
有一个fn new(path: &String) -> Box<TraitN>
。new
创建和self.path = path.to_string();
设置.
在一些 impl fn doit(&self) { ... }
for 中StructX
,我想调用tokio::fs::File::open(&self.path)
.
我怎么能过&self.path
一辈子'static
?
这是一个完整的例子:
extern crate futures;
extern crate tokio;
#[macro_use]
extern crate error_chain;
use futures::future;
use futures::future::{loop_fn, ok, Future, Loop};
use futures::Stream;
use std::io::BufReader;
use tokio::{fs, io};
mod error {
error_chain!{}
}
use error::*;
type FutureResult<T> = future::FutureResult<T, Error>;
trait HandlerTrait {
fn new(path: &str) -> Box<HandlerTrait>
where
Self: Sized;
fn get_all(&self) -> FutureResult<Vec<String>>;
}
#[derive(Debug)]
pub struct Handler {
path: String,
}
impl HandlerTrait for Handler {
fn new(path: &str) -> Box<HandlerTrait> {
Box::new(Handler {
path: path.to_string(),
})
}
fn get_all(&self) -> FutureResult<Vec<String>> {
let file = fs::File::open(self.path.clone())
.and_then(|file: fs::File| ok(file))
.wait()
.unwrap();
let lines = io::lines(BufReader::new(file));
ok(lines
.filter(|line| line.len() > 80)
.map(|all| all[0..80].to_string())
.collect()
.wait()
.unwrap())
}
}
fn get_handler(path: &str) -> Option<Box<HandlerTrait>> {
Some(Handler::new(path))
}
fn get_path() -> FutureResult<String> {
ok("./somepath/file".to_string())
}
fn start_runtime() -> Result<()> {
let path: &str = get_path().wait().unwrap().as_str();
tokio::run(doit(path.clone()));
Ok(())
}
fn doit(path: &'static str) -> impl Future<Item = (), Error = ()> + 'static {
let n = 0;
loop_fn(n, move |_nr| {
let lh = get_handler(path).unwrap();
lh.get_all()
.or_else(|_| Err(()))
.and_then(|_all| ok(Loop::Break(())))
})
}
#[test]
fn test() {
start_runtime().unwrap();
assert!(true);
}
error[E0597]: borrowed value does not live long enough
--> src/lib.rs:63:22
|
63 | let path: &str = get_path().wait().unwrap().as_str();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ - temporary value only lives until here
| |
| temporary value does not live long enough
|
= note: borrowed value must be valid for the static lifetime...