blob: 9cea604d27e29c0c58404bb22fe1cf38378a54b5 [file] [log] [blame]
//! Using `select!` to send and receive on the same channel at the same time.
//!
//! This example is based on the following program in Go.
//!
//! Source:
//! - https://web.archive.org/web/20171209034309/https://www.nada.kth.se/~snilsson/concurrency
//! - http://www.nada.kth.se/~snilsson/concurrency/src/matching.go
//!
//! Copyright & License:
//! - Stefan Nilsson
//! - Creative Commons Attribution 3.0 Unported License
//! - https://creativecommons.org/licenses/by/3.0/
//!
//! ```go
//! func main() {
//! people := []string{"Anna", "Bob", "Cody", "Dave", "Eva"}
//! match := make(chan string, 1) // Make room for one unmatched send.
//! wg := new(sync.WaitGroup)
//! for _, name := range people {
//! wg.Add(1)
//! go Seek(name, match, wg)
//! }
//! wg.Wait()
//! select {
//! case name := <-match:
//! fmt.Printf("No one received %s’s message.\n", name)
//! default:
//! // There was no pending send operation.
//! }
//! }
//!
//! // Seek either sends or receives, whichever possible, a name on the match
//! // channel and notifies the wait group when done.
//! func Seek(name string, match chan string, wg *sync.WaitGroup) {
//! select {
//! case peer := <-match:
//! fmt.Printf("%s received a message from %s.\n", name, peer)
//! case match <- name:
//! // Wait for someone to receive my message.
//! }
//! wg.Done()
//! }
//! ```
extern crate crossbeam;
#[macro_use]
extern crate crossbeam_channel;
use crossbeam_channel::bounded;
fn main() {
let people = vec!["Anna", "Bob", "Cody", "Dave", "Eva"];
let (s, r) = bounded(1); // Make room for one unmatched send.
// Either send my name into the channel or receive someone else's, whatever happens first.
let seek = |name, s, r| {
select! {
recv(r) -> peer => println!("{} received a message from {}.", name, peer.unwrap()),
send(s, name) -> _ => {}, // Wait for someone to receive my message.
}
};
crossbeam::scope(|scope| {
for name in people {
let (s, r) = (s.clone(), r.clone());
scope.spawn(move || seek(name, s, r));
}
});
// Check if there is a pending send operation.
if let Ok(name) = r.try_recv() {
println!("No one received {}’s message.", name);
}
}