How to create a `CoroutineScope` that is a child of another ? What I tried: ```val parentScope = ......

# coroutines

[tseisel]

How to create a CoroutineScope that is a child of another ?
What I tried:

val parentScope = ...
val childScope = parentScope + SupervisorJob()

parentScope.cancel()
parentScope.isActive // false
childScope.isActive // true (!!)

It seems that cancelling the parent does not cancel its children. I guess I'm missing something here...

[bezrukov]

val childScope = parentScope + SupervisorJob(parentScope.coroutineContext[Job])

[bezrukov]

it attaches child job to parent job

[Javier Troconis]

Woudln't this make them siblings rather than enforce a parent-child hierarchy?

[Dennis]

Isn't it just either
coroutineScope (doc) or supervisorScope (doc)

[Dennis]

Well this doesn't return the scope to you, right.

[bezrukov]

@Javier Troconis nope, it will be parent-child hierarchy, if you cancel childScope, parentScope will be active active.
From the SupervisorJob doc:

* If [parent] job is specified, then this supervisor job becomes a child job of its parent and is cancelled when its parent fails or is cancelled. All this supervisor's children are cancelled in this case, too. The invocation of [cancel][Job.cancel] with exception (other than [CancellationException]) on this supervisor job also cancels parent.

[Javier Troconis]

Thanks @bezrukov. Thought that it was simply setting the job itself and not the parent

[tseisel]

Indeed, that was the missing part!
I expected the child scope to directly inherit the job of its parent. It seems that this parent-child relationship should be explicitly defined

[bezrukov]

I think it's impossible because constructor can't be suspend, and there is no access to coroutineContext from non-suspend block.