From 7a8c91630d7105f09e35cc9a1f8c3197391e0b98 Mon Sep 17 00:00:00 2001 From: asborisjuas Date: Tue, 28 Nov 2023 18:40:57 +0300 Subject: [PATCH] Add example of reading from closed channel --- examples/closing-channels/closing-channels.go | 6 ++++ .../closing-channels/closing-channels.hash | 4 +-- examples/closing-channels/closing-channels.sh | 9 ++++-- public/closing-channels | 31 +++++++++++++++---- 4 files changed, 40 insertions(+), 10 deletions(-) diff --git a/examples/closing-channels/closing-channels.go b/examples/closing-channels/closing-channels.go index 926d9b5..b00fff7 100644 --- a/examples/closing-channels/closing-channels.go +++ b/examples/closing-channels/closing-channels.go @@ -47,4 +47,10 @@ func main() { // [synchronization](channel-synchronization) approach // we saw earlier. <-done + + // It is possible to read from an empty closed channel, + // but instead of waiting for a message, we will + // immediately receive a zero value of the channel's type. + j := <-jobs + fmt.Println("no jobs to receive", j) } diff --git a/examples/closing-channels/closing-channels.hash b/examples/closing-channels/closing-channels.hash index 3e33a07..1079571 100644 --- a/examples/closing-channels/closing-channels.hash +++ b/examples/closing-channels/closing-channels.hash @@ -1,2 +1,2 @@ -8f26c901e0f14df2ca40329a354c3ac86a5c3a07 -vCvRjcMq7p3 +56d8d399e304cdf5ab36663b43397ca43126e260 +cNvXGNi9l27 diff --git a/examples/closing-channels/closing-channels.sh b/examples/closing-channels/closing-channels.sh index 013f8a8..99cb663 100644 --- a/examples/closing-channels/closing-channels.sh +++ b/examples/closing-channels/closing-channels.sh @@ -7,6 +7,11 @@ sent job 3 received job 3 sent all jobs received all jobs +no jobs to receive 0 -# The idea of closed channels leads naturally to our next -# example: `range` over channels. +# Be sure that channel is not closed when you read +# from it, especially when iterating over a channel. +# Otherwise you might get an unexpected result or +# even enter an infinite loop. +# To learn how to correctly use `range` over channels, +# see our next example. diff --git a/public/closing-channels b/public/closing-channels index a631097..186dcb3 100644 --- a/public/closing-channels +++ b/public/closing-channels @@ -43,7 +43,7 @@ completion to the channel’s receivers.

- + 
package main
@@ -125,10 +125,24 @@ channel, then closes it.

synchronization approach we saw earlier.

+ + + + 
    <-done
+ + + + + +

It is possible to read from an empty closed channel, +but instead of waiting for a message, you will +immediately return zero value of the channel’s type.

+ - 
    <-done
+          
    j := <-jobs
+    fmt.Println("no jobs to receive", j)
 }

           
         
@@ -151,14 +165,19 @@ we saw earlier.

 sent job 3
 received job 3
 sent all jobs
-received all jobs
+received all jobs +no jobs to receive 0 -

The idea of closed channels leads naturally to our next -example: range over channels.

+

Be sure that channel is not closed when you read +from it, especially when iterating over a channel. +Otherwise you might get an incorrect result or +even enter an infinite loop. +To learn how to correctly use range over channels, +see our next example.

@@ -182,7 +201,7 @@ example: range over channels.