rxswift error handle issue

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.