Swift AsyncStream variable, use after finish() - swift

Question

I'm currently reading about AsyncStreams and as I understand it, they are best for tasks that produce some results over time, but have a lifespan - e.g. start and end. Here's an example I am playing with:
struct AHardWorkingStruct {
lazy var updates = AsyncStream<String> { continuation in
onProgress = { value in
continuation.yield(value)
}
onFinish = { value in
continuation.yield(value)
continuation.finish()
}
}
private var onProgress: (String) -> Void = { _ in () }
private var onFinish: (String) -> Void = { _ in () }
func doSomeWork() async {
let numbers = (0..<20).map { anInt in
anInt^2
}
for number in numbers {
onProgress("The number is \(number)")
if(number == 20) {
onFinish("I'm DONE!")
}
}
}
}
I then have AHardWorkingStruct as a property in my view controller and use it like so:
class MyViewController: UIViewController {
var myHardWorker = AHardWorkingStruct()
#IBAction func tapToRun(_ sender: UIButton) {
Task {
await myHardWorker.doSomeWork()
}
}
override func viewDidLoad() {
super.viewDidLoad()
Task {
for await stream in myHardWorker.updates {
print(stream)
}
}
}
This works perfectly when I tap the button.
However, once I call finish() on the stream, I no longer get the updates from it - which I understand is expected behaviour.
My question is, how can I keep getting updates from a stream that is a variable on a long-lived object? Is there a "reset"? (other than getting rid of the lazy and nilling the variable)
I also have a 2nd part to this - what would be the best way to unit test an asyncstream? I've tried using expectations, but not sure if this is right.