[go-nuts] How to check a channel is closed or not without reading it?

On 19/04/2013, at 11:38 PM, Reck Hou wrote:

Please read this article first:

http://stackoverflow.com/questions/16105325/how-to-check-a-channel-is-closed-or-not-without-reading-it


"So I think the best way to solve this is worker() close channel when exits, if the controller finds a channel closed, it will jump over it and do nothing. But I can't find how to check a channel is already closed or not in this situation. If I try to read the channel in controller, the controller might be blocked. So I'm very confused for now."

PS: Recovering the raised panic is what I have tried, but it will close goroutine which raised panic. In this case it will be controller so it's no use.

Still, I think it's useful for go team to implement this function in next version of Go.

--
You received this message because you are subscribed to the Google Groups "golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
For more options, visit https://groups.google.com/groups/opt_out.

On Fri, Apr 19, 2013 at 9:38 PM, Reck Hou wrote:

Please read this article first:


http://stackoverflow.com/questions/16105325/how-to-check-a-channel-is-closed-or-not-without-reading-it

"So I think the best way to solve this is worker() close channel when
exits, if the controller finds a channel closed, it will jump over it and
do nothing. But I can't find how to check a channel is already closed or
not in this situation. If I try to read the channel in controller, the
controller might be blocked. So I'm very confused for now."

PS: Recovering the raised panic is what I have tried, but it will close
goroutine which raised panic. In this case it will be controller so it's no
use.

Still, I think it's useful for go team to implement this function in next
version of Go.

On Friday, April 19, 2013 9:38:14 AM UTC-4, Reck Hou wrote:

Please read this article first:


http://stackoverflow.com/questions/16105325/how-to-check-a-channel-is-closed-or-not-without-reading-it


"So I think the best way to solve this is worker() close channel when
exits, if the controller finds a channel closed, it will jump over it and
do nothing. But I can't find how to check a channel is already closed or
not in this situation. If I try to read the channel in controller, the
controller might be blocked. So I'm very confused for now."

PS: Recovering the raised panic is what I have tried, but it will close
goroutine which raised panic. In this case it will be controller so it's no
use.

Still, I think it's useful for go team to implement this function in next
version of Go.

What good would checking if a channel is closed be? Even if a check
returns that a channel is open, it could be closed between the check and
when you use it.

On 19 April 2013 14:50, Reck Hou wrote:

My thought was if a channel is closed, I will jump over & remove it. But I
can't read it to check whether it's closed or not since it will be blocked
and whole controller will halt in my case.

On Fri, Apr 19, 2013 at 3:59 PM, chris dollin wrote:
`x, ok = <- ch` does not block.

There may be reasons this isn't what you actually want to
do, but blocking isn't one of them.

Chris

--
Chris "allusive" Dollin

--
You received this message because you are subscribed to the Google Groups
"golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an
email to [email protected].
For more options, visit https://groups.google.com/groups/opt_out.

On Fri, Apr 19, 2013 at 4:02 PM, Péter Szilágyi wrote:

Yes it will.

The solution is:

select {
case x, ok := <- ch
// Do something
default:
// Non blocking part
}

On 19 April 2013 15:02, Péter Szilágyi wrote:

Yes it will.

On 19/04/2013, at 11:37 PM, "chris dollin" wrote:

I had to re-read the paragraph in the spec three times before I
realised I had read it so drastically wrong.

On Fri, Apr 19, 2013 at 9:50 PM, Reck Hou wrote:

My thought was if a channel is closed, I will jump over & remove it. But I
can't read it to check whether it's closed or not since it will be blocked
and whole controller will halt in my case.