When I add the `suspend` modifier to a function th...

# coroutines

[Pere Casafont]

When I add the suspend modifier to a function that I know it will take long to compute, intellij bugs me with the Redundant 'suspend' modifier inspection. Am I doing something wrong? All I want is to force this function to be called from a coroutine scope...

[gildor]

Yes, suspend doesn’t mean that it would somehow make blocking code non-blocking, but you can use withContext(<http://Dispatchers.IO/Defatult|Dispatchers.IO/Defatult>) { someBlockingCode } to move work out of current thread to some IO/Computation dispatcher

[gildor]

Do you have an example of such code?

[Pere Casafont]

So let's imagine I have

fun calculateExpensiveHash() {
  // computations taking 500-1500ms
}

I just want to enforce it being called from a coroutine scope, and to do so I'd add the suspend modifier...

[Eric Martori]

if your function is not suspending or calling other suspending function it doesn't make sense to mark it as a suspend function.
You can use withContext which will suspend the calling funtion untill your computation completes:

suspend fun foo() = withContext(<http://Dispatchers.IO|Dispatchers.IO>){
    //expensive computation IO computation that returns 1
    1
}

[Pere Casafont]

alright, thank you

[gildor]

If it's a computation (so CPU bound task, not a some IO operation), so probably better to use Dispatchers.Default which CPU-bound dispatcher)

[Pere Casafont]

right, I had gotten it 🙂

[bdawg.io]

Also, if you just want to force a CoroutineScope (for some reason?) you can also make it an extension function fun CoroutineScope.calculateExpensiveHash() = ...

[Pere Casafont]

thanks