অ্যাসিঙ্ক রাউটারের জন্য লেখার সময় আমি অ্যাসিঙ্ক ফাংশনগুলি পরিচালনা করতে পারি না hyper।
এই কোড:
use std::collections::HashMap;
use std::future::Future;
type BoxedResult<T> = Result<T, Box<dyn std::error::Error + Send + Sync>>;
type CalcFn = Box<dyn Fn(i32, i32) -> dyn Future<Output = BoxedResult<i32>>>;
async fn add(a: i32, b: i32) -> BoxedResult<i32> {
Ok(a + b)
}
async fn sub(a: i32, b: i32) -> BoxedResult<i32> {
Ok(a - b)
}
fn main() {
let mut map: HashMap<&str, CalcFn> = Default::default();
map.insert("add", Box::new(add));
map.insert("sub", Box::new(sub));
println!("map size: {}", map.len());
}
নিম্নলিখিত সংকলক ত্রুটি উত্পন্ন করে:
error[E0271]: type mismatch resolving `<fn(i32, i32) -> impl std::future::Future {add} as std::ops::FnOnce<(i32, i32)>>::Output == dyn std::future::Future<Output = std::result::Result<i32, std::boxed::Box<dyn std::error::Error + std::marker::Send + std::marker::Sync>>>`
--> src/main.rs:17:23
|
17 | map.insert("add", Box::new(add));
| ^^^^^^^^^^^^^ expected opaque type, found trait std::future::Future
|
= note: expected type `impl std::future::Future`
found type `dyn std::future::Future<Output = std::result::Result<i32, std::boxed::Box<dyn std::error::Error + std::marker::Send + std::marker::Sync>>>`
= note: required for the cast to the object type `dyn std::ops::Fn(i32, i32) -> dyn std::future::Future<Output = std::result::Result<i32, std::boxed::Box<dyn std::error::Error + std::marker::Send + std::marker::Sync>>>`
error[E0271]: type mismatch resolving `<fn(i32, i32) -> impl std::future::Future {sub} as std::ops::FnOnce<(i32, i32)>>::Output == dyn std::future::Future<Output = std::result::Result<i32, std::boxed::Box<dyn std::error::Error + std::marker::Send + std::marker::Sync>>>`
--> src/main.rs:18:23
|
18 | map.insert("sub", Box::new(sub));
| ^^^^^^^^^^^^^ expected opaque type, found trait std::future::Future
|
= note: expected type `impl std::future::Future`
found type `dyn std::future::Future<Output = std::result::Result<i32, std::boxed::Box<dyn std::error::Error + std::marker::Send + std::marker::Sync>>>`
= note: required for the cast to the object type `dyn std::ops::Fn(i32, i32) -> dyn std::future::Future<Output = std::result::Result<i32, std::boxed::Box<dyn std::error::Error + std::marker::Send + std::marker::Sync>>>`
দেখে মনে হচ্ছে impl Futureএবং এর মধ্যে দ্বন্দ্ব রয়েছে dyn Future, তবে কীভাবে এটি পরিচালনা করব আমার কোনও ধারণা নেই।