How add dynamic values in Kotlin Flow

Question

if we know list values to be processed in Kotlin flow then we can follow the below function

  flow {
          (1..1000).forEach {
            delay(1000) //Process Data
            emit(it.toLong())
          }
       }.collect{
            delay(2000)
            print(it)
        }

where we know we are going to print values from 1 to 1000

In my case, I do not have input value at the beginning of the flow. I want to start the flow when I have value 1 and start the process of the data meanwhile if I have a new value then I have to add it in Queue wait till value 1 gets processed then start the process of the new value.

Basically, I want to add value outside of the flow block, Is any solution available to achieve that?

score 3 · Accepted Answer · answered Jul 06 '21 at 10:49

You can use a SharedFlow for that with a buffer. It would be something like this:

val myFlow = MutableSharedFlow<Long>()

You can emit values like this:

(1..1000).forEach {
    delay(1000) //Process Data
    println("Emitting $it")
    myFlow.emit(it.toLong())
}

And collect them like this:

myFlow
    .buffer()
    .collect {
        delay(2000)
        println("Received: $it")
    }

If you don't use the buffer operator, every time you emit a value, the emision gets suspended until collect finishes its work.

How add dynamic values in Kotlin Flow

1 Answers1