Converting suspendCancellableCoroutine into callbackFlow

October 5, 2022

I have the following function.

 suspend fun result() = suspendCancellableCoroutine<Int> {continuation ->
      val callback = object : Callback {
            continuation.resume(value)
      }
 }

and then I call result in a Coroutine as follows:

 someCoroutine {
     when (result()){
          x -> doSomething
          y -> doSomething
           ...
     }
 }

It works, but I keep getting the error when its called again:

Uncaught exception: Already resumed, but proposed with update.

I figured I need a callbackFlow instead, but I’m not too sure as to how to implement it. Here’s what I have so far.

 suspend fun result() = callbackFlow<Int> {
      val callback = object : Callback {
            trySendBlocking(value)
      }
      awaitClose()
 }

I’m guessing I have to use collect(), but I don’t know how to process it in the coroutine. Any help would be appreciated.

>Solution :

To use values emitted by Flow you need to use one of the terminal operators, for example collect:

coroutineScope.launch {
   result().collect { value ->
       when (value) {
          x -> doSomething
          y -> doSomething
          ...
       }
   }
}