# [−] [src] Macro tokio::try_join

    macro_rules! try_join {
        (@ {
            // One `_` for each branch in the `try_join!` macro. This is not used once
            // normalization is complete.
            ( $($count:tt)* )

            // Normalized try_join! branches
            $( ( $($skip:tt)* ) $e:expr, )*

        }) => { ... };
        (@ { ( $($s:tt)* ) $($t:tt)* } $e:expr, $($r:tt)* ) => { ... };
        ( $($e:expr),* $(,)?) => { ... };
    }

Wait on multiple concurrent branches, returning when all branches complete with `Ok(_)` or on the first `Err(_)`.

The `try_join!` macro must be used inside of async functions, closures, and blocks.

Similar to `join!`, the `try_join!` macro takes a list of async expressions and evaluates them concurrently on the same task. Each async expression evaluates to a future and the futures from each expression are multiplexed on the current task. The `try_join!` macro returns when all branches return with `Ok` or when the first branch returns with `Err`.

# Notes

The supplied futures are stored inline and does not require allocating a `Vec`.

### Runtime characteristics

By running all async expressions on the current task, the expressions are able to run concurrently but not in parallel. This means all expressions are run on the same thread and if one branch blocks the thread, all other expressions will be unable to continue. If parallelism is required, spawn each async expression using `tokio::spawn` and pass the join handle to `try_join!`.

# Examples

Basic try_join with two branches.

    async fn do_stuff_async() -> Result<(), &'static str> {
        // async work
    }

    async fn more_async_work() -> Result<(), &'static str> {
        // more here
    }

    #[tokio::main]
    async fn main() {
        let res = tokio::try_join!(
            do_stuff_async(),
            more_async_work());

        match res {
             Ok((first, second)) => {
                 // do something with the values
             }
             Err(err) => {
                println!("processing failed; error = {}", err);
             }
        }
    }