Can I make a `Deferred lt A gt ` `NonCancelable` by wrapping

Question

Can I make a `Deferred lt A gt ` `NonCancelable` by wrapping and awaiting it in a `withContext` block like below And how does its scope get re wired correctly Snippet seems to work although I don t quite understand it ``` val def = thisWasPassedToMe val result = withContext NonCancelable def await ```

bdawg.io · Answer

You will still get a `CancellationException` thrown if the backing Job for `def` gets cancelled

bdawg.io · Answer

`NonCancellable` will just make sure that your `withContext` itself doesn t exit from being cancelled itself

simon.vergauwen · Answer

I m not sure I 100 understand that last bit Only what gets created within `withContext` is NonCancelable

simon.vergauwen · Answer

Is there another way to make an existing Deferred NonCancelable

bdawg.io · Answer

No a `Deferred` is just a reference handle to the state of the coroutine

simon.vergauwen · Answer

Alright thanks Guess I ll have to work around it

groostav · Answer

< simon vergauwen> whats the parent coroutine factory assumjing its either a `launch` or `runBlocking` you can use `CoroutineStart ATOMIC`

groostav · Answer

eg ``` launch CoroutineStart ATOMIC val def = thisWasPassedToMe def await ```

groostav · Answer

also of course finally blocks function through cancellation ``` suspend fun doStuffWithThingPassedToMe try val def = thisWasPassedToMe finally this will fire in all cercomstances except abandonment ```

simon.vergauwen · Answer

I need it for this function <https github com arrow kt arrow blob master modules effects arrow effects kotlinx coroutines data src main kotlin arrow effects coroutines DeferredK kt L442>

simon.vergauwen · Answer

It s within a suspend function However this `Deferred` is guaranteed to have never run

groostav · Answer

sorry so your calling this library function or your looking for an implementation of `release`

groostav · Answer

its funny I ve read the scala red book but I still dont understand arrow

simon.vergauwen · Answer

The point of this function is to acquire some resource This resource is provided through a `Deferred lt A gt ` that has never run and is lazily run

simon.vergauwen · Answer

acquire is guaranteed not to be cancelled and the `release` is guaranteed to be called There is also a `use` function which you can use to consume the `acquire`d resource

simon.vergauwen · Answer

In other words you can use this function to compose different lazily run `Deferred` to safely consume and release resources with a guarantee not to leak

simon.vergauwen · Answer

We use this to provide a generic API for data types with similar behaviours like `Observable` `Flux` `IO`

simon.vergauwen · Answer

If you have any questions about Arrow feel free to swing by < C5UPMM0A0|arrow> to ask questions and we ll be glad to help