How would you guys wrap a `Callable` in a coroutine?

# coroutines

[expensivebelly]

How would you guys wrap a Callable in a coroutine?

[Joffrey]

What do you mean exactly? You want to run a coroutine that asynchronously executes the Callable? What is your goal more precisely?

[expensivebelly]

I have a Cache that uses a Java get(K key, Callable<V> valueLoader) but I would like to be able to call it with this signature: suspend fun get(key: K, valueLoader: suspend () -> V)

[Joffrey]

The first part of the problem is that the original method calls the Callable in a synchronous way. It blocks its current thread in order to get the value, so there is no way you can provide this value asynchronously and lazily at the same time. The solution for this part would be to use `runBlocking`:

fun get(key: K, valueLoader: suspend () -> V) = get(key, Callable { runBlocking { valueLoader() } })

You wanted your new function to be suspend probably because you want to express the asynchronism for this. The problem is that the original get is synchronous, so you cannot really wait for its value in a suspending way. With runBlocking, you don't really have to anyway.

[Sam]

If you use an async cache like Caffeine, you can make the whole thing fully asynchronous

[Sam]

My current best attempt for how to do it is in this StackOverflow answer

[expensivebelly]

I'll try Caffeine, currently I'm using this one https://github.com/dropbox/Store/tree/main/cache

[Sam]

It should be very familiar since it looks like both are based on Guava

[expensivebelly]

I see, it's a lot of code to get a Kotlin cache working that's synchronised by key

[expensivebelly]

Thanks for info