Hi guys! There are scopes, like `ViewModelScope` f...

# coroutines

[ubu]

Hi guys! There are scopes, like ViewModelScope from AAC, which works best for most of simple use cases, but when you want to cancel the job whose lifecycle is very specific, then there is a place for discussion. Suppose an operation should be run starting from onStart() call until there is a onStop() call. What would you suggest as good practice here to control this operation’s lifecycle?

I started by creating custom scope, inside which this operation would run, then i realised, that after cancellation this scope can’t be re-used. Then I thought that creating a new scope every time onStart() is called is a bad idea (or not?). So I switched to a nullable variable holding a reference to a Job created after launch { ... } in onStart(), which I cancel in onStop(). Seems normal, but what if you want to cancel a lot of different jobs between `onStart()`/()`onStop()` calls? I might want a strange thing to do: having a scope, which, when you cancel it, cancel all its children job, but could be reset to allow new coroutines to run. Perhaps, I do not understand properly which logic stands behind not allowing to re-use cancelled scope.

Thanks!

[Erik]

Simplest solution is what you said:
lifecycleScope.launch {} a bunch of `Job`s in onStart and cancel them in onStop.

To keep track of all jobs at once, just use a class property private val jobs = mutableListOf<Job>() and simply add jobs to it: jobs += lifecycleScope.launch {}.

in onStop just jobs.forEach { it.cancel() } (which could be a nice extension on Collection<Job>)

[Erik]

And probably you should also jobs.clear() in onStop