UIAlertController not working with Rx-Single - ios

Question

So, I added this extension function to the PrimitiveSequenceType to show a loader on screen when making a network call
extension PrimitiveSequenceType where Trait == SingleTrait {
func subscribeWithLoader(showLoaderOn viewController: MyUIViewController, onSuccess: ((Element) -> Void)? = nil, onFailure: ((Swift.Error) -> Void)? = nil)-> Disposable {
let loader = viewController.showLoading()
return subscribe { (element) in
DispatchQueue.main.async {
loader.dismiss(animated: true, completion: {
onSuccess?(element)
})
}
} onFailure: { (error) in
DispatchQueue.main.async {
loader.dismiss(animated: true, completion: {
onFailure?(error)
})
}
}
}
}
Here is my showLoading function
func showLoading()-> UIAlertController {
let alert = UIAlertController(title: nil, message: "Please wait...", preferredStyle: .alert)
let loadingIndicator = UIActivityIndicatorView(frame: CGRect(x: 10, y: 5, width: 50, height: 50))
loadingIndicator.hidesWhenStopped = true
loadingIndicator.style = UIActivityIndicatorView.Style.medium
loadingIndicator.startAnimating();
alert.view.addSubview(loadingIndicator)
present(alert, animated: true, completion: nil)
return alert
}
But the loader never stops. Can anybody let me know what I'm doing wrong. Any help would be appreciated.

Answer 1

It's not very Rx like, but it works... except for one edge case. You dismiss the alert on success and on failure, but what if the Single is disposed without emitting either? Then the alert won't dismiss.
Try something like this instead:
extension PrimitiveSequenceType where Trait == SingleTrait {
func withLoader(showLoaderOn viewController: UIViewController) -> Single<Element> {
func loadingController() -> UIAlertController {
let alert = UIAlertController(title: nil, message: "Please wait...", preferredStyle: .alert)
let loadingIndicator = UIActivityIndicatorView(frame: CGRect(x: 10, y: 5, width: 50, height: 50))
loadingIndicator.hidesWhenStopped = true
loadingIndicator.style = UIActivityIndicatorView.Style.medium
loadingIndicator.startAnimating();
alert.view.addSubview(loadingIndicator)
return alert
}
return Single.create { fullfil in
let loader = loadingController()
viewController.present(loader, animated: true)
let disposable = self.subscribe(fullfil)
return Disposables.create {
disposable.dispose()
loader.dismiss(animated: true)
}
}
}
}
If you like wrapping view controllers up like this. Check out this library... Cause-Logic-Effect

Answer 2

So, I end up adding a delay like this
extension PrimitiveSequenceType where Trait == SingleTrait {
func subscribeWithLoader(showLoaderOn viewController: MyUIViewController, onSuccess: ((Element) -> Void)? = nil, onFailure: ((Swift.Error) -> Void)? = nil)-> Disposable {
let loader = viewController.showLoading()
return subscribe { (element) in
onSuccess?(element)
DispatchQueue.global().asyncAfter(deadline: .now() + 0.5, execute: {
DispatchQueue.main.async {
loader.dismiss(animated: true, completion: nil)
}
})
} onFailure: { (error) in
onFailure?(error)
DispatchQueue.global().asyncAfter(deadline: .now() + 0.5, execute: {
DispatchQueue.main.async {
loader.dismiss(animated: true, completion: nil)
}
})
} onDisposed: {
DispatchQueue.global().asyncAfter(deadline: .now() + 0.5, execute: {
DispatchQueue.main.async {
loader.dismiss(animated: true, completion: nil)
}
})
}
}
}
I think the problem was onSuccess (that means calling loader.dismiss) was getting called even before UIAlertController could show itself. So, by adding a delay of 500ms solves the issue the UIAlertController is going to have enough time to show itself, and then we are dismissing it.
Open to new ideas and improvements.