我正在开发旨在与 TcpStream 或 stdin/stdout 一起使用的网络服务。我得到一个编译错误:the trait tokio::io::util::async_read_ext::AsyncReadExt cannot be made into an object
.目前我的解决方法是使用包装枚举:
enum ClientReader {
Stream(OwnedReadHalf),
Stdin(Stdin),
}
enum ClientWriter {
Stream(OwnedWriteHalf),
Stdout(Stdout),
}
这需要 match
到处都是 block ,看起来很不雅。我做了一个简化的项目来重现这个问题:
cargo .toml
[package]
name = "demo"
version = "0.1.0"
authors = ["test"]
edition = "2018"
[dependencies]
tokio = { version = "0.2", features = ["full"] }
src/main.rsuse tokio::io::AsyncReadExt;
struct Test {
test: Box<dyn AsyncReadExt>,
}
fn main () {}
这会产生类似的错误:error[E0038]: the trait `tokio::io::AsyncReadExt` cannot be made into an object
--> src/main.rs:4:3
|
4 | test: Box<dyn AsyncReadExt>,
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `tokio::io::AsyncReadExt` cannot be made into an object
|
::: /home/???/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-0.2.22/src/io/util/async_read_ext.rs:162:12
|
162 | fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> Read<'a, Self>
| ---- the trait cannot be made into an object because method `read` references the `Self` type in its return type
...
280 | fn read_exact<'a>(&'a mut self, buf: &'a mut [u8]) -> ReadExact<'a, Self>
| ---------- the trait cannot be made into an object because method `read_exact` references the `Self` type in its return type
我不确定如何进行。我在考虑一个巨人 impl
enum
的 block 包装器,但这似乎比 match
block 。在 OO 语言中会有一个父类或接口(interface),所以我调查了 trait_enum
自动制作包装器的 crate impl
但是让它发挥作用有很多麻烦。目前,我确定唯一可行的清理方法是将解决方法移动到宏或函数中。
我将不胜感激有关更好方法的任何反馈。 :)
编辑:根据 user4815162342 的建议,我将结构泛型设置为
AsyncReadExt
这似乎适用于我的示例。稍后将尝试我的更大项目。use tokio::io::AsyncReadExt;
struct Test<T: AsyncReadExt> {
test: T,
}
async fn myfn<T: AsyncReadExt>(mut t: Test<T>) where T: std::marker::Unpin {
let mut v = Vec::<u8>::new();
t.test.read_buf(&mut v).await;
}
fn main () {}
最佳答案
转 AsyncRead
到一个 trait 对象,你应该使用类型 Pin<Box<dyn AsyncRead>>
.
use std::pin::Pin;
use tokio::io::AsyncRead;
struct Test {
test: Pin<Box<dyn AsyncRead>>,
}
impl Test {
fn new<T: AsyncRead>(io: T) -> Self {
Self {
test: Box::pin(io),
}
}
}
AsyncReadExt
trait 是一个扩展 trait,你应该总是使用 AsyncRead
提及 AsyncRead
的类型时的特征.
关于rust - 尝试使用 dyn AsyncReadExt, "the trait cannot be made into an object"错误,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/63626508/