英文:
Go non-blocking channel send, test-for-failure before attempting to send?
问题
有没有一种方法可以在不实际尝试发送的情况下测试 Go 通道发送的失败？标准的非阻塞发送代码如下：
msg := "hi"
select {
case messages <- msg:
fmt.Println("sent message", msg)
default:
fmt.Println("no message sent")
}
问题是，为了测试通道，我需要准备好要发送的 "msg"。
我想测试发送是否会失败，而不需要准备好要发送的 "msg"。
英文:
Is there a way to test for failure of a go channel send without actually attempting the send? The standard non-blocking send is like so:
msg := "hi"
select {
case messages <- msg:
fmt.Println("sent message", msg)
default:
fmt.Println("no message sent")
}
The problem is that I need to have "msg" ready to send in order to test the channel.
I would like to test to see if a send will fail in a way that does not require having "msg" ready for sending.
答案1
得分: 7
在一般情况下，这样做没有好处，因为这样会导致竞争条件。在生成消息后，通道可能不再准备好发送。
如果你需要这种模式，你可以使用第二个用于信号传递的通道：
select {
case <-ready:
msg := generateMsg()
messages <- msg
fmt.Println("sent message", msg)
default:
fmt.Println("no message sent")
}
或者你可以使用 sync.Cond。
英文:
That would do no good in the general case, since you then have a race. After generating msg the channel may no longer be ready to send.
If you need this pattern, you either need a second channel for signaling,
select {
case <-ready:
msg := generateMsg()
messages <- msg
fmt.Println("sent message", msg)
default:
fmt.Println("no message sent")
}
or you can use a sync.Cond
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