swift - RxSwift 和 MVVM : observable not executing without binding

Question

我是 RxSwift 的新手，正在尝试使用 MVVM 架构实现应用程序。我有 View 模型:

class CategoriesViewModel {

fileprivate let api: APIService
fileprivate let database: DatabaseService

let categories: Results<Category>

// Input
let actionRequest = PublishSubject<Void>()

// Output
let changeset: Observable<(AnyRealmCollection<Category>, RealmChangeset?)>
let apiSuccess: Observable<Void>
let apiFailure: Observable<Error>

init(api: APIService, database: DatabaseService) {
    self.api = api
    self.database = database

    categories = database.realm.objects(Category.self).sorted(byKeyPath: Category.KeyPath.name)

    changeset = Observable.changeset(from: categories)

    let requestResult = actionRequest
        .flatMapLatest { [weak api] _ -> Observable<Event<[Category]>> in
            guard let strongAPI = api else {
                return Observable.empty()
            }

            let request = APIService.MappableRequest(Category.self, resource: .categories)
            return strongAPI.mappedArrayObservable(from: request).materialize()
        }
        .shareReplayLatestWhileConnected()

    apiSuccess = requestResult
        .map { $0.element }
        .filterNil()
        .flatMapLatest { [weak database] newObjects -> Observable<Void> in
            guard let strongDatabase = database else {
                return Observable.empty()
            }

            return strongDatabase.updateObservable(with: newObjects)
        }

    apiFailure = requestResult
        .map { $0.error }
        .filterNil()
}

}

我在 View Controller 中有以下 bininds:

   viewModel.apiSuccess
        .map { _ in false }
        .bind(to: refreshControl.rx.isRefreshing)
        .disposed(by: disposeBag)

    viewModel.apiFailure
        .map { _ in false }
        .bind(to: refreshControl.rx.isRefreshing)
        .disposed(by: disposeBag)

但是如果我评论绑定(bind)，数据库更新部分将停止执行。无论如何我都需要让它执行，而不是在 View 模型中使用处理包。可能吗？

还有一点额外的问题:我应该像在我的代码中那样使用 api/database 和 return Observable.empty()查看模型代码，或者我可以安全地使用 unowned api/unowned database 吗？

谢谢。

更新:

APIService 中可观察到的返回函数:

func mappedArrayObservable<T>(from request: MappableRequest<T>) -> Observable<[T]> {
    let jsonArray = SessionManager.jsonArrayObservable(with: request.urlRequest, isSecured: request.isSecured)
    return jsonArray.mapResponse(on: mappingSheduler, { Mapper<T>().mapArray(JSONArray: $0) })
}

Answer 1

除非有订阅者准备接收结果，否则工作不会完成。

你的 DatabaseService 需要有一个 dispose 包并订阅 Observable<[Category]> .像这样的东西:

class ProductionDatabase: DatabaseService {

    var categoriesUpdated: Observable<Void> { return _categories }

    func updateObservable(with categories: Observable<[Category]>) {
        categories
            .subscribe(onNext: { [weak self] categories in
                // store categories an then
                self?._categories.onNext()
            })
            .disposed(by: bag)
    }

    private let _categories = PublishSubject<Void>()
    private let bag = DisposeBag()
}

然后 apiSuccess = database.categoriesUpdated和 database.updateObservable(with: requestResult.map { $0.element }.filterNil())