How to configure a Bool Stream in RxSwift

Question

I am willing to force a reload of a collectionView when new content is fetched from a web-service while using RxSwift. I can't figure out why I don't receive an event on newContent with the following code when my onComplete closure is properly called.

class ListingView : UIView {

    var newContentStream: Observable<Bool>?
    let disposeBag = DisposeBag()

    @IBOutlet weak var collectionView: UICollectionView!

    weak var viewModel: ListingViewModel?

    func bind(viewModel: ListingViewModel) {
        self.viewModel = viewModel
    }

    func configure() {
        guard let viewModel = self.viewModel else { return }

        self.newContentStream = viewModel.newContent.asObservable()
        self.newContentStream!.subscribeNext { _ in
            self.collectionView.reloadData()
        }
        .addDisposableTo(self.disposeBag)
    } 
}

and then within my viewModel:

class ListingViewModel {
    let dataSource = ListingViewDataSoure()
    var newContent = Variable(false)

    func mount() {
        let onComplete : ([item]? -> Void) = { [weak self] items  in
            self?.dataSource.items = items
            self?.newContent = Variable(true)
        }

        guard let URL = API.generateURL() else { return }
        Requestor.fetchAll(onComplete, fromURL: URL)
    }
}

Answer 1

It's because self?.newContent = Variable(true) is replacing the newContent with an entirely new Variable, after you've already subscribed to the original here:

self.newContentStream = viewModel.newContent.asObservable()
self.newContentStream!.subscribeNext { ......

That subscription in your UIView is now listening to an Observable that no one is ever going to be sending a Next event on.

Instead, you should be sending out a Next event on the current (and only) newContent Variable/Observable:

self?.newContent.value = true

You could fix it and continue to use a newContent Variable and a reloadData call, however, I wouldn't recommend doing it like this. Instead, check out RxDataSources.