3 ms·
> Is the select semantically different than something like this? Yes. select can do a lot of things. It's overloaded to be something like 5 different things.
by TheDong 7y ago
> Is the select semantically different than something like this?
Yes. select can do a lot of things. It's overloaded to be something like 5 different things. Here, let me show you:
chanOne := make(chan int)
chanTwo := make(chan int)
ctx := context.Background()
// Receive whichever is ready first. Blocking
select {
case v := <-chanOne:
case v := <-chanTwo:
}
// Non-blocking read
select {
case v := <-chanOne:
default:
}
// Timeout and cancellation
select {
case v := <-chanOne:
case <-time.After(1 * time.Second):
// timeout
case <-ctx.Done():
// cancel
}
// Write or read, whichever channel is ready first
select {
case chanOne <- 1:
case v := <-chanTwo:
}
Another form of cancellation is closing channels, which causes reads to return the zero value immediately, and causes any writes to that closed channel to immediately panic (effectively abort the program).
- jayd16 7y agoNeat. Most of the permutations are easily handled in other languages as well except for the full blocking (sleeping) case. Without a channel the scheduler can reason about, most languages would have to busy wait or possibly pull from multiple channels.
- SamReidHughes 7y agoI think the biggest advantage is that it's a lot harder to screw up using a select statement than most equivalent API's you'd create in other languages that allow waiting on one of N channels/signals/channel/event operations, and branching based off that. Simply because you're either constructing a bunch of callback objects or you get some number N saying the Nth parameter had an event, and your code has to match N to the specific channel correctly.