How to conditionally observe and bind with RxSwift

Question

I'm trying to observe a Variable and when some property of this variable fits a condition, I want to make an "observable" API call and bind the results of that call with some UI element. It is working the way I present it here, but I'm having the thought that it could be implemented way better, because now I'm nesting the subscription methods:

self.viewModel.product
    .asObservable()
    .subscribe { [weak self](refreshProduct) in

        self?.tableView.reloadData()
        self?.marketProduct.value.marketProduct = refreshProduct.element?.productId

        if refreshProduct.element?.stockQuantity != nil {

            self?.viewModel.getUserMarketCart()
                .map({ (carts) -> Bool in
                    return carts.cartLines.count > 0
                }).bind(onNext: { [weak self](isIncluded) in
                    self?.footerView.set(buyable: isIncluded)
                }).disposed(by: (self?.disposeBag)!)
        }
    }.disposed(by: disposeBag)

Is there any other way to do this? I can get a filter on the first observable, but I don't understand how I can call the other one and bind it on the UI.

NOTE: I excluded a few other lines of code for code clarity.

I think you should have 2 observers: 1st for table reloading, 2nd for binding new data to your `self?.footerView`. Just split current realization. — biloshkurskyi.ss, Dec 12 '17 at 09:47
The thing is that they need to be sync, when a new event comes, I need to reload the table and update my UI with the data of the API call. — sheinix, Dec 12 '17 at 10:45

score 0 · Answer 1 · answered Dec 14 '17 at 13:32

A typical solution would be using .switchLatest() as follows.

create *let switchSubject = PublishSubject<Observable<Response>>()"
bind UI to it's latest value: switchSubject.switchLatest().bind(...
update 'switchSubject' with new requests: switchSubject.onNext(newServiceCall)

How to conditionally observe and bind with RxSwift

1 Answers1