rxswift error handle issue - swift

Question

I have a BehaviorSubject named createObservable in my view model. And my view controller subscribe it.
viewModel!.createObservable.subscribe(onNext: {[unowned self] (obj:PassbookModelType?) -> Void in
if let _ = obj{
self.dismissVC()
}
}, onError: { (error) -> Void in
print(error)
}).addDisposableTo(self.dispose)
I have a function named saveObject() also in the view model. If I click the navigation bar right item it will be emitted. And there is an error will send to createObservable's observer.
func saveObject(){
```````
```````
if condition {
createObservable.on(Event.Next(model))
createObservable.onCompleted()
}else{
createObservable.onError(MyError.someError)
}
}
The problem is that if the error happened the createObservable will be closed, so I won't receive any Next event in the future. I tried to use retry(), but it seems will cause deadlock, view controller can't response any touch event any more. So can some one tell me how to fix this issue? Thanks a lot
viewModel!.createObservable.retry().subscribe(onNext: {[unowned self] (obj:PassbookModelType?) -> Void in
if let _ = obj{
self.dismissVC()
}
}, onError: { (error) -> Void in
print(error)
}).addDisposableTo(self.dispose)

Answer 1

I suggest to make the type of createObservable PublishSubject<Observable<PassbookModelType>>, instead of BehaviorSubject<PassbookModelType?> which, I guess, accidentally flattens two Rx streams conceptually separatable each other: the saveObject process itself (an one-shot process) and starting the saveObject process initiated by user action repeatedly. I've written a short example to demonstrate it.
let createObservable = PublishSubject<Observable<Int>>()
override func viewDidLoad() {
super.viewDidLoad()
createObservable.flatMap {
$0.map { obj in
print("success: \(obj)")
}
.catchError { err in
print("failure: \(err)")
return empty()
}
}.subscribe()
}
// Simulates an asynchronous proccess to succeed.
#IBAction func testSuccess(sender: UIView!) {
let oneShot = PublishSubject<Int>()
createObservable.onNext(oneShot)
callbackAfter3sec { res in
oneShot.onNext(1)
oneShot.onCompleted()
}
}
// Simulates an asynchronous process to fail.
#IBAction func testFailure(sender: UIView!) {
let oneShot = PublishSubject<Int>()
createObservable.onNext(oneShot)
callbackAfter3sec { res in
oneShot.onError(NSError(domain: "Error", code: 1, userInfo: nil))
}
}
func callbackAfter3sec(completion: Int -> ()) {
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, Int64(NSEC_PER_SEC * 3)), dispatch_get_main_queue()) {
completion(2)
}
}
There is an important merit with that: If the one-shot process would become in the Rx style (for example, like as callbackAfter3sec() -> Observable<Int>) in the future, there were no need to re-write the use-side code like in the viewDidLoad above. There is an only one change to do is to pass an Observable<> object to createObservable.onNext(...).
Sorry for my poor English skill. I hope this makes sense to you.