Trait to identify senders of channels

help
1

I have a use case, where I want to accept either Sender or SyncSender or whatever else can .send() a specific type through a channel.

Is there a trait in std that I'm overlooking here?

I currently roll my own helper trait

use crate::request::Request;
use std::sync::mpsc::{SendError, Sender, SyncSender};

/// A trait to identify types that can be used as `ASHv2` hosts.
pub trait Host {
    /// Send a request to the transceiver.
    ///
    /// # Errors
    ///
    /// Returns a [`SendError`] if the request could not be sent.
    fn send(&self, request: Request) -> Result<(), SendError<Request>>;
}

impl Host for Sender<Request> {
    fn send(&self, request: Request) -> Result<(), SendError<Request>> {
        Self::send(self, request)
    }
}

impl Host for SyncSender<Request> {
    fn send(&self, request: Request) -> Result<(), SendError<Request>> {
        Self::send(self, request)
    }
}

But would like to use something existing if available.

2

It doesn’t appear so— The list of traits implemented for Sender is pretty short, and nothing stands out.

3

Alternatively, instead of building a "use-once" trait, you can use simple closure callbacks, preferably FnOnce or FnMut:

fn use_sender(send: impl FnOnce(Request) -> Result<(), Request>) {
    if let Err(not_sent) = send(Request::new(...)) {
        todo!()
    }
}

fn caller() {
    let (tx, rx) = channel();
    let send = move |msg| {
        tx.send(msg).unwrap();
        Ok(())
    };
    use_sender(send);
}

This technique allows the caller to adapt your functionality easily. The caller can even store the value in a variable:

fn caller() {
    let mut store = None;

    let send = |msg| {
        store = Some(msg);
        Ok(())
    };

    use_sender(send); // Maybe a message is sent, maybe not...

    match store {
        Some(msg) => handle_the_message(msg), // We got a message
        None => no_message_sent(),
    }
}

This approach offers flexibility, allowing the caller to adapt to different situations without needing a custom trait.

4

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