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What are the uses of an empty struct?

Answer»

Empty struct is used when we want to SAVE memories. This is because they do not consume any memory for the values. The syntax for an empty struct is:

a := struct{}{}

The size of empty struct would return 0 when using println(unsafe.Sizeof(a))

The important use of empty struct is to show the developer that we do not have any value. The purpose is purely informational. Some of the examples where the empty struct is useful are as follows:

  • While implementing a data set: We can use the empty struct to implement a dataset. Consider an example as shown below.
map_obj := make(map[string]struct{})for _, value := range []string{"interviewbit", "golang", "QUESTIONS"} { map_obj[value] = struct{}{}}fmt.Println(map_obj)

The output of this code would be:

map[interviewbit:{} golang:{} questions:{}]

Here, we are initializing the value of a key to an empty struct and initializing the map_obj to an empty struct.

  • In graph traversals in the map of tracking visited vertices. For example, consider the below piece of code where we are initializing the value of vertex visited empty struct.
visited := make(map[string]struct{})for _, isExists := visited[v]; !isExists { // First time VISITING a vertex. visited[v] = struct{}{}}
  • When a CHANNEL needs to send a signal of an event without the need for sending any data. From the below piece of code, we can see that we are sending a signal using sending empty struct to the channel which is sent to the workerRoutine.
func workerRoutine(ch chan struct{}) { // Receive message from main program. <-ch println("Signal Received") // Send a message to the main program. close(ch)}func main() { //Create channel ch := make(chan struct{}) //define workerRoutine GO workerRoutine(ch) // Send signal to worker goroutine ch <- struct{}{} // Receive a message from the workerRoutine. <-ch println(“Signal Received") }

The output of the code would be:

Signal ReceivedSignal Received


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