Today I needed this: ```class SuspendAtomicRef<T : Any> { private var data: T? = null ...

# coroutines

[spand]

Today I needed this:

class SuspendAtomicRef<T : Any> {
    private var data: T? = null
    private val mutex = Mutex()

    suspend fun getOrSet(init: suspend () -> T): T {
        return mutex.withLock {
            data ?: init().also { data = it }
        }
    }
}

Seems pretty basic so I wonder if I am missing it in the coroutines library?

[Dominaezzz]

Odd, why not just use an atomic ref? Would be faster.

[spand]

It for an optimization so reducing multiple init invocations the entire point of it

[Dominaezzz]

Ah, I missed the init part.

[Dominaezzz]

Given you still hit the mutex even after initialisation, there's still much room for improvement.

[Dominaezzz]

I also feel like I would refactor my code to not need this but that's probably just ignorance due to lack of use case.

[ephemient]

https://github.com/Kotlin/kotlinx.coroutines/issues/706

[spand]

Thanks for the hint @ephemient. I was actually using Louis suspendLazy previously but it sucks for properties. I think my SuspendAtomicRef work better in that:
1. Needs no coroutine on allocation (great for properties)
2. Supports cancellation much better in that a cancelled init will not break or block the others waiting.