rust - StreamExt::forward失败，错误为 `expected integer, found enum ` std::result::Result``

我正在尝试将 rust future 流(重复)连接到水槽(排水)。
第一种方法可以正常工作(请在下面检查)，但是第二种方法使用.forward无法编译(内联显示错误)。关于我在做什么错的任何指示？

use futures::stream::StreamExt;
use futures::sink::SinkExt;
use futures::executor;

fn main() {
    executor::block_on( async {
        // works
        let mut work = futures::stream::repeat(5);
        let mut drain = futures::sink::drain();
        match drain.send(work.next()).await {
            Ok(_r) => println!("Done"),
            Err(_e) => println!("Error"),
        };

        // works
        let res: Vec<i32> = futures::stream::repeat(5).take(3).collect::<Vec<i32>>().await;
        println!("{:?}", res);

        // doesn't work
        // futures::stream::repeat(5).forward(futures::sink::drain());
        //                            ^^^^^^^ expected integer, found enum `std::result::Result`
        //  error[E0271]: type mismatch resolving `<futures_util::stream::repeat::Repeat<{integer}> as futures_core::stream::Stream>::Item == std::result::Result<_, _>`

        // Fixed above with repeat(Ok(5)) but not repeat(5)
        match futures::stream::repeat(Ok(5)).take(3).forward(futures::sink::drain()).await {
            Ok(_r) => println!("Done"),
            Err(_e) => println!("Error"),
        };
    });
}

https://docs.rs/futures/0.3.1/futures/sink/fn.drain.html

https://docs.rs/futures/0.3.1/futures/stream/trait.StreamExt.html#method.forward

最佳答案

我想你想要更多这样的东西吗？

use futures::stream::StreamExt;
use futures::sink::SinkExt;

#[tokio::main]
async fn main() {
    // works
    let mut work = futures::stream::repeat(5);
    let mut drain = futures::sink::drain();
    match drain.send(work.next()).await {
        Ok(_r) => println!("Done"),
        Err(_e) => println!("Error"),
    };
    // doesn't work

    futures::stream::repeat(Ok(5)).forward(futures::sink::drain());
}

正如错误(稍有混淆)所说明的那样，在这种情况下，重复调用必须采用Result参数。

关于rust - StreamExt::forward失败，错误为 `expected integer, found enum ` std::result::Result``，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/59751192/