我正在尝试将rust futures流(repeat)连接到一个接收器(drain)。
第一种方法很好地工作(请参见以下内容),但第二种使用.forward
的方法无法编译(错误显示在行内)。有什么指针可以告诉我我做错了什么吗?
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"),
};
});
}
相关文档
- https://docs.rs/futures/0.3.1/futures/stream/fn.repeat.html - 重复地产生给定的元素。
- https://docs.rs/futures/0.3.1/futures/sink/fn.drain.html - 将所有输入项都丢弃掉,直到接收者准备就绪。
- https://docs.rs/futures/0.3.1/futures/stream/trait.StreamExt.html#method.forward - 将此流的所有项发送到提供的sink中。