Hi, I see a lot of examples for attaching `CoroutineScope` to Android lifecycles with a pattern like...

# coroutines

[uli]

Hi,
I see a lot of examples for attaching CoroutineScope to Android lifecycles with a pattern like that:

class UiLifecycleScope : CoroutineScope, LifecycleObserver {

    private lateinit var job: Job
    override val coroutineContext: CoroutineContext
        get() = job + Dispatchers.Main

    @OnLifecycleEvent(Lifecycle.Event.ON_START)
    fun onCreate() {
        job = Job()
    }

Do you guys see any reason for constructing the context with a getter, creating a new context every time.
How about making the scope var?

override lateinit var coroutineContext: CoroutineContext
    @OnLifecycleEvent(Lifecycle.Event.ON_START)
    fun onCreate() {
        coroutineContext = Dispatchers.Main + Job()
    }

[withoutclass]

I think the suggested way now is using https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/-main-scope.html

[withoutclass]

https://medium.com/@streetsofboston/much-has-changed-since-the-addition-of-structured-concurrency-for-coroutines-1788ba203466

[uli]

Sure. But all this does not work if you want to cancel in onStop. Then your activity might get restarted but your scope is cancelled. That's why you have to inject a new Job()

[louiscad]

What you want is something like createScope here, or just that: https://github.com/LouisCAD/Splitties/tree/master/modules/lifecycle-coroutines

[uli]

Thanks @louiscad. I'll take a look. But this does not answer the question. I am not looking for a solution but for clarification.
The pattern I described is everywhere on Google but seems to be second best. That's what I am trying to understand

[louiscad]

You should call your job/scope startedJob/Scope for explicitness.

[louiscad]

Creating a new context/scope each time doesn't seem good to me. I'd just create a scope on each onStart call, and do what I need there, possibly launching child coroutines.

[uli]

I'd rather say rootJob. After I call cancel it is no longer started

[uli]

@louiscad thanks, creating a new context in onStart is what I thought. Just too bad about every example out there goes with a context getter

[withoutclass]

you can also use cancelChildren and keep the root job around iirc

[uli]

Interesting. Didn't think of it yet.
But then I'd have to keep the job around

[louiscad]

cancelChildren would let coroutines started after onStop run before onStart is called again, and until the second onStop call though