Kotlin: Should a job be passed along with a dispatcher while creating a coroutine scope

Question

I am doing

 private val uiScope = CoroutineScope(Dispatchers.Main)

to create a coroutinescope and using that to launch the coroutines in my fragment.

uiScope.launch {
        withContext(Dispatchers.Default) {
            ....
        }
        ....
    }

I do a cancel on uiScope when the fragment is detached from window. While creating the uiScope should i be passing a job() as well?

Answer 1

The documentation of fun CoroutineScope is clear on this:

If the given context does not contain a Job element, then a default Job() is created. This way, cancellation or failure or any child coroutine in this scope cancels all the other children, just like inside coroutineScope block.

Using a job that propagates the failure of its children is not the best choice for the top-level scope. You should instead use the MainScope factory function. It takes no arguments and constructs exactly the scope you need. From the docs:

The resulting scope has SupervisorJob and Dispatchers.Main context elements.