有关进入频道的一些问题

Question

1-what is the condition that make chan break?

deliveries <-chan amqp.Delivery
for d:= range deliveries{
    ..
}

If there is no more data in chan deliveries about a few minutes,that it will break. Is the code up is same to below?

deliveries <- chan amqp.Delivery
for{
    d,ok:=<-deliveries
    if !ok{
        break
    }
    //code
}

2-Why does chan not only return data but also status?And what does the "ok" mean?

3-How does the chan realize?"ok" is the status about client,Why can it return the "ok"?

Answer 1

I will answer question 2 and 3 first because the answer provides context for my answer to question 1.

2, 3) The builtin function close(c) records that no more values will be sent to the channel c.

The second result in a receive expression is a bool indicating if the operation was successful. The second result is true if a sent value was received or false if the zero value was received because the channel was closed.

1) Range over a channel receives values sent on the channel until the channel is closed.

The following loops are very similar. They both receive values until the channel is closed.

for v := range c {
     // code
}

for {
    v, ok := <-c
    if != ok {
        break
    }
    // code
}

The main difference between these loops is the scope of of the variable v. The scope of v is outside of the first loop and inside the second loop. This distinction is important if you use a closure and goroutine in the loop.