`RefCell<std::string::String>`不能在线程之间安全地共享? [英] `RefCell<std::string::String>` cannot be shared between threads safely?
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问题描述
这是
解决方案
RefCell 仅适用于单线程.您将需要使用类似但适用于多个线程的互斥锁.您可以在此处阅读有关互斥锁的更多信息:https://doc.rust-lang.org/std/sync/struct.Mutex.html.
以下是移动 Arc
use std::sync::{Arc, Mutex};fn 主(){让 mut 测试:Arc>= Arc::new(Mutex::from(Foo".to_string()));让 mut test_for_closure = Arc::clone(&test);让闭包 = ||异步移动{//锁定它，使其不能在其他线程中使用让 foo = test_for_closure.lock().unwrap();println!("{}", foo);};} This is a continuation of How to re-use a value from the outer scope inside a closure in Rust? , opened new Q for better presentation.
// main.rs
// The value will be modified eventually inside `main`
// and a http request should respond with whatever "current" value it holds.
let mut test_for_closure :Arc<RefCell<String>> = Arc::new(RefCell::from("Foo".to_string()));
// ...
// Handler for HTTP requests
// From https://docs.rs/hyper/0.14.8/hyper/service/fn.service_fn.html
let make_svc = make_service_fn(|_conn| async {
Ok::<_, Infallible>(service_fn(|req: Request<Body>| async move {
if req.version() == Version::HTTP_11 {
let foo:String = *test_for_closure.borrow();
Ok(Response::new(Body::from(foo.as_str())))
} else {
Err("not HTTP/1.1, abort connection")
}
}))
});
Unfortunately, I get RefCell<std::string::String> cannot be shared between threads safely:
解决方案
RefCell only works on single threads. You will need to use Mutex which is similar but works on multiple threads. You can read more about Mutex here: https://doc.rust-lang.org/std/sync/struct.Mutex.html.
Here is an example of moving an Arc<Mutex<>> into a closure:
use std::sync::{Arc, Mutex};
fn main() {
let mut test: Arc<Mutex<String>> = Arc::new(Mutex::from("Foo".to_string()));
let mut test_for_closure = Arc::clone(&test);
let closure = || async move {
// lock it so it cant be used in other threads
let foo = test_for_closure.lock().unwrap();
println!("{}", foo);
};
}
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