channel

问题 I have one channel and the receiver is main. I spawn multiple goroutines that each send a string over the channel. Now, this causes a deadlock because I didn't close the channel properly using the close function. The thing is, I have no idea how many goroutines will be created, so there's no way to know when to close the channel. I've tried using WaitGroup, the problem is, I've read that I can't use Add in the goroutine and that I should use wg.Add(1) in the main process/goroutine, I've tried

问题 I would like to create my hyperledger fabric network but I face an error when I try to create a channel. error on outputChannelCreateTx: Cannot define a new channel with no Application section My configtx file has of course application section, so I dont know what else can be the reason for. 回答1: Application has to be defined or referenced under the channel in the profile and also have an Application section if using *ApplicationDefaults. Profiles: ... ExampleChannel: Consortium:

问题 I am trying to create a jigsaw puzzle and I need to mask the UIImages to obtain the puzzle pieces. I don't understand how can I mask a JPG picture because as I understand it doesn't have an alpha channel. Can anyone help me with this? The JPGs are on an online server and there is no way to download them as PNG. And one more thing, I can’t find this function anywhere on the Apple documentation: “CopyImageAndAddAlphaChannel”. Does it even exist. I found a few references on some forums but

问题 I'm learning Go, and have run across the following code snippet: package main import "fmt" func sum(a []int, c chan int) { sum := 0 for _, v := range a { sum += v } c <- sum // send sum to c } func main() { a := []int{7, 2, 8, -9, 4, 0} c := make(chan int, 2) go sum(a[0:3], c) go sum(a[3:6], c) x := <-c y := <-c // x, y := <-c, <-c // receive from c fmt.Println(x, y) } Output: -5 17 Program exited. Can someone please tell me why the 2nd calling of the "sum" function is coming through the

问题 somehow I dont catch the Spring-Integration Metrics Content. What I want to have is a statistical output about, how many message/second goes through a message channel, what is the min and the max throughput. If I use newTicketChannel.getSendRate() , then I become following output: What is clear to me is N (number of Messages). Mean for me is the number of messages what have been progressed each second (?). But what is totally unclear to me are the values of min and max . I need something like

问题 From my understanding of Go scheduler, Go scheduling algorithm is partially preemptive: goroutine switches happen when a goroutine is calling a function or blocking on I/O. Does a goroutine switch happen when sending a message to a channel? // goroutine A ch <- message // some additional code without function calls // goroutine B message := <- ch In the code above, I want the code after ch <- message in A to be executed before switching to B, is this guaranteed? or does B get scheduled right

问题 I love the way Go handles I/O multiplexing internally which epoll and another mechanisms and schedules green threads (go-routine here) on its own giving the freedom to write synchronous code. I know TCP sockets are non-blocking and read will give EAGAIN when no data is available. Given that, conn.Read(buffer) will detect this and blocks the go routine doing a connection read with no data available in the socket buffer . Is there a way to stop such go routine without closing the underlying

问题 I need to start a number of workers with single task queue and single result queue. Each worker should be started in different goroutine. And I need to wait till all workers will be finished and task queue will be empty before exiting from program. I have prepare small example for goroutine synchronization. The main idea was that we count tasks in queue and waiting for all workers to finish jobs. But current implementation sometime miss values. Why this happends and how to solve the problem?

问题 I am trying to use a slice chan type inside a struct, similar to the code below. However, when I try to receive at test := <-c.slice The program hangs. Is there a way to do this? package main import "fmt" type blah struct { slice chan [][]int } func main() { slice := make([][]int, 3) c := blah{make(chan [][]int)} slice[0] = []int{1, 2, 3} slice[1] = []int{4, 5, 6} slice[2] = []int{7, 8, 9} go func() { test := <- c.slice test = slice c.slice <- test }() fmt.Println(<-c.slice) } 回答1: The first

问题 Let's take this example from the GoTour, as it illustrates my problem with processing SDL events only when there are events. package main import ( "fmt" "time" ) func main() { tick := time.Tick(1e8) boom := time.After(5e8) for { select { case <-tick: fmt.Println("tick.") case <-boom: fmt.Println("BOOM!") return default: fmt.Println(" .") time.Sleep(5e7) } } } This works. But what if I don't want to print or sleep in the default case, but just want to keep looping? I tried this: case <-boom: