方法 for_each 存在，但使用 StreamDeckSocket 时不满足 trait bounds

Question

我正在尝试使用 streamdeck-rs 板条箱，但无法让 example code 工作。

我的实现基本上是给出的确切示例：

use futures::future::Future;
use std::env;
use streamdeck_rs::registration::*;
use streamdeck_rs::socket::StreamDeckSocket;

//the fields of these structs doesn't matter
struct GlobalSettings {}
struct ActionSettings {}
struct MessageToSd {}
struct MessageFromSd {}

fn register() {
    let params = RegistrationParams::from_args(env::args()).unwrap();
    let connect =
        StreamDeckSocket::<GlobalSettings, ActionSettings, MessageFromSd, MessageToSd>::connect(
            params.port,
            params.event,
            params.uuid,
        );
    tokio::run(
        connect
            .map_err(|e| println!("connection failed: {:?}", e))
            .and_then(|socket| {
                socket
                    .for_each(|message| println!("recieved: {:?}", message))
                    .map_err(|e| println!("read error: {:?}", e))
            }),
    );
}

我的错误消息会根据我导入的内容而变化，但它始终是“方法for_each 存在但不满足以下特征界限”的变体。对于我现在列出的导入，我的错误消息是：

error[E0599]: no method named `for_each` found for type `streamdeck_rs::socket::StreamDeckSocket<GlobalSettings, ActionSettings, MessageFromSd, MessageToSd>` in the current scope
  --> src/main.rs:37:35
   |
37 |         .and_then(|socket| socket.for_each(|message| println!("recieved: {:?}", message))
   |                                   ^^^^^^^^
   |
   = note: the method `for_each` exists but the following trait bounds were not satisfied:
           `&mut streamdeck_rs::socket::StreamDeckSocket<GlobalSettings, ActionSettings, MessageFromSd, MessageToSd> : std::iter::Iterator`

---

我可以导入future::Stream：

use streamdeck_rs::registration::*;
use streamdeck_rs::socket::StreamDeckSocket;
use std::env;
use futures::future::Future;
use futures::Stream;
//rest same as before

我得到这个错误：

error[E0599]: no method named `for_each` found for type `streamdeck_rs::socket::StreamDeckSocket<GlobalSettings, ActionSettings, MessageFromSd, MessageToSd>` in the current scope
  --> src/main.rs:37:35
   |
37 |         .and_then(|socket| socket.for_each(|message| println!("recieved: {:?}", message))
   |                                   ^^^^^^^^
   |
   = note: the method `for_each` exists but the following trait bounds were not satisfied:
           `&mut streamdeck_rs::socket::StreamDeckSocket<GlobalSettings, ActionSettings, MessageFromSd, MessageToSd> : futures::stream::Stream`
           `&mut streamdeck_rs::socket::StreamDeckSocket<GlobalSettings, ActionSettings, MessageFromSd, MessageToSd> : std::iter::Iterator`
           `streamdeck_rs::socket::StreamDeckSocket<GlobalSettings, ActionSettings, MessageFromSd, MessageToSd> : futures::stream::Stream`



warning: unused import: `futures::Stream`

还要注意有关未使用导入的警告。

因为 StreamDeckSocket 是在 crate 中定义的，所以我无法在其上实现任何特征。

我知道这个问题以几种形式存在，但据我了解，这些答案仅适用于我正在使用的 crate 中缺少 trait 实现的情况。

Answer 1

示例代码 sn-p 不太对，但很接近：

• 结构需要#[derive(Deserialize, Debug)]
• 根据the documentation，传递给for_each 的闭包类型错误。

以下编译：

use futures::future::Future;
use futures::stream::Stream;
use serde::Deserialize;
use std::env;
use streamdeck_rs::registration::*;
use streamdeck_rs::socket::StreamDeckSocket;

#[derive(Deserialize, Debug)]
struct GlobalSettings {}

#[derive(Deserialize, Debug)]
struct ActionSettings {}

#[derive(Deserialize, Debug)]
struct MessageToSd {}

#[derive(Deserialize, Debug)]
struct MessageFromSd {}

fn main() {
    let params = RegistrationParams::from_args(env::args()).unwrap();
    let connect =
        StreamDeckSocket::<GlobalSettings, ActionSettings, MessageFromSd, MessageToSd>::connect(
            params.port,
            params.event,
            params.uuid,
        );
    tokio::run(
        connect
            .map_err(|e| println!("connection failed: {:?}", e))
            .and_then(|socket| {
                socket
                    .for_each(|message| {
                        println!("recieved: {:?}", message);
                        Ok(())
                    })
                    .map_err(|e| println!("read error: {:?}", e))
            }),
    );
}