tokio::select! how to handle multiple branch.

[kenmasumitsu]

Hi,

tokio::select! need to declare all async operations at the compile time.
If the async operations are not known in compile time, can I use tokio::select! ?

   // size of receivers is unknown at the compile time.
    let receivers: Vec<mpsc::Receiver<u32>> = Vec::new();
    receivers.push(rx1);
    receivers.push(rx2);
    ... 
  
    loop {
       tokio::select! {
           // how to monitor all Receivers in receivers ? 
       }
    }

I want like FD_SET in C.

[Darksonn]

If you have a variable number of streams, then you shouldn't be using select!. Here are some other options:

1. Have all the senders send to the same receiver so you only have to receive from one thing.
2. Use tokio_stream::StreamMap.
3. Use futures::stream::SelectAll.

The difference between option 2 and 3 is whether it tells you which receiver the message came from.

[kenmasumitsu]

Thanks for kindly quick response. I will check the option 2 and 3.

[Darksonn]

To use either solution, you are going to need the ReceiverStream wrapper.

[kenmasumitsu]

I will check it, too. I really appreciate your support.

[Noah-Kennedy]

If the futures all have the same output type, there is the select_all function in the futures crate: https://docs.rs/futures/0.3.17/futures/future/fn.select_all.html