Rust循环中借用值生命周期不足问题求助

我在实现Redis到ZMQ的重广播器时，卡在了循环中处理PubSub消息生成的临时值的生命周期问题上。我知道问题出在哪，但就是没法生成ZMQ发布者需要的Vec<&String>，试过改类型、克隆各种操作，还是一直碰到所有权和生命周期相关的错误。

问题代码 #

async fn ps_rebroadcaster() -> Result<(), ApiError>{

    let mut inproc_publisher: async_zmq::Publish<std::vec::IntoIter<&std::string::String>, &std::string::String>  = async_zmq::publish("ipc://pricing")?.bind()?;
    
    let con_str = &APP_CONFIG.REDIS_URL;
    let conn = create_client(con_str.to_string())
        .await
        .expect("Can't connect to redis");
    let mut pubsub = conn.get_async_connection().await?.into_pubsub();
    match pubsub.psubscribe("T1050_*").await {
        Ok(_) => {}
        Err(_) => {}
    };

    let mut msg_stream = pubsub.into_on_message();
     
    loop {
        let result = msg_stream.next().await;
        match result {
            Some(message) => {
                 
                let channel_name = message.get_channel_name().to_string();
                let payload_value: redis::Value = message.get_payload().expect("Can't get payload of message");
                let payload_string: String = FromRedisValue::from_redis_value(&payload_value).expect("Can't convert from Redis value");
                
                let item: Vec<&String> = vec![&channel_name , &payload_string  ];
                // problem here  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 

                inproc_publisher.send(item.into()).await?;
            }
            None => {
                println!("None received");
                continue;
            }
        }
    }

}

错误信息 #

error[E0597]: `channel_name` does not live long enough
   --> src/server.rs:248:47
    |
248 |                 let item: Vec<&String> = vec![&channel_name , &payload_string  ];
    |                                               ^^^^^^^^^^^^^ borrowed value does not live long enough
249 |                 
250 |                 inproc_publisher.send(item.into()).await?;
    |                 ---------------------------------- borrow later used here
251 |             }
    |             - `channel_name` dropped here while still borrowed

error[E0597]: `payload_string` does not live long enough
   --> src/server.rs:248:63
    |
248 |                 let item: Vec<&String> = vec![&channel_name , &payload_string  ];
    |                                                               ^^^^^^^^^^^^^^^ borrowed value does not live long enough
249 |                 
250 |                 inproc_publisher.send(item.into()).await?;
    |                 ---------------------------------- borrow later used here
251 |             }
    |             - `payload_string` dropped here while still borrowed

问题根源 #

你定义的inproc_publisher类型要求接收引用类型的消息，但channel_name和payload_string都是循环块内的局部变量，生命周期只到当前循环迭代结束。ZMQ的send是异步操作，编译器无法保证这些引用在异步操作完成前还能存活，因此抛出生命周期错误。

解决方法 #

直接改用拥有所有权的String类型构造消息，避免引用带来的生命周期问题：

修改后的代码 #

async fn ps_rebroadcaster() -> Result<(), ApiError>{
    // 调整发布者类型为接收String的迭代器
    let mut inproc_publisher: async_zmq::Publish<std::vec::IntoIter<String>, String> = 
        async_zmq::publish("ipc://pricing")?.bind()?;
    
    let con_str = &APP_CONFIG.REDIS_URL;
    let conn = create_client(con_str.to_string())
        .await
        .expect("Can't connect to redis");
    let mut pubsub = conn.get_async_connection().await?.into_pubsub();
    
    // 不要忽略订阅错误，可添加日志或错误处理
    if pubsub.psubscribe("T1050_*").await.is_err() {
        eprintln!("Failed to subscribe to T1050_* channels");
    };

    let mut msg_stream = pubsub.into_on_message();
     
    loop {
        let result = msg_stream.next().await;
        match result {
            Some(message) => {
                let channel_name = message.get_channel_name().to_string();
                let payload_value = message.get_payload().expect("Can't get payload of message");
                let payload_string = FromRedisValue::from_redis_value(&payload_value)
                    .expect("Can't convert from Redis value");
                
                // 直接构造Vec<String>，无需借用
                let item = vec![channel_name, payload_string];
                inproc_publisher.send(item.into()).await?;
            }
            None => {
                println!("None received");
                continue;
            }
        }
    }
}

额外优化建议 #

• 不要忽略psubscribe、get_payload等操作的错误，可将expect替换为?并在ApiError中添加对应的错误变体，实现统一错误处理
• 可添加日志记录关键步骤，方便后续排查问题

内容的提问来源于stack exchange，提问作者mike_t