CODEWITHSUNDEEP
androidkotlinconcurrencysocket.iokotlin-coroutines
ArcDexx
ArcDexx

Reputation: 483

Wait for async result inside synchronous function

I need to return a value within an asynchronous callback. This value is acquired asynchronously as a websocket acknowledgement, and I can't find a way to block that callback's execution until the value is retrieved... I have tried all combinations of coroutines to no avail.

override fun someAsyncCallback() : String 
{
   var myAsyncValue = ""

   socket.emit(event = "someEvent", callback = { result ->
       //This is an asynchronous callback
       myAsyncValue = result
   })

   //Insert way to wait for the async value to be set 
   
   return myAsyncValue
}

Upvotes: 2

Views: 799

Answers (1)

Tenfour04
Tenfour04

Reputation: 93639

Presumably the function is called from a thread where it's OK to block. You can use a CountDownLatch to wait for it.

override fun someAsyncCallback() : String 
{
   var myAsyncValue = ""
   val latch = CountDownLatch(1)

   socket.emit(event = "someEvent", callback = { result ->
       myAsyncValue = result
       latch.countDown()
   })

   latch.await()
   
   return myAsyncValue
}

You can also pass a timeout to the latch.await() method so this doesn't block indefinitely.

Upvotes: 2

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