ios - rxSwift Observable 依赖

Question

我是 rxSwift 的新手。我有 3 个可观察对象，checkAccount、fetchMails 和 fetchFolders。
fetchMails 和 fetchFolders 取决于 checkAccount 结果。如何使用 UIButton Tap 调用 fetchMails 和 fetchFolders 操作？如果 checkAccount 成功，我不会在每次 fetchMails 和 fetchFolders 时运行它。如果 checkAccount 失败，我想在 fetchMails 和 fetchFolders 时重试 checkAccount。我怎样才能达到这个目的？这是我的代码:

@IBOutlet weak var btn1: UIButton!
@IBOutlet weak var btn2: UIButton!
var checkAccountO: Observable<Bool>?
let bag = DisposeBag()

let fetchO: Observable<[String]> = Observable.create { observer in
        DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(1000)) {
            observer.onNext(["1","2"])
        }
        return Disposables.create()
    }

let fetchFolderO: Observable<[String]>  =  Observable.create { observer in
        DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(1000)) {
            observer.onNext(["folder1","folder2"])
        }
        return Disposables.create()
    }
override func viewDidLoad() {
    super.viewDidLoad()

    fetchFolders().subscribe { (evetn) in
        print("folders \(evetn)")
    }.addDisposableTo(bag)

    fetchMails().subscribe { (evetn) in
        print("mails \(evetn)")
    }.addDisposableTo(bag)
}

func checkAccount() -> Observable<Bool> {
    if let ob = checkAccountO {
        return ob
    }
    checkAccountO = Observable.create { (observer) -> Disposable in
        print("checking...")
        DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(1000)) {
            let i = arc4random() % 2
            if i == 0 {
                print("succ")
                observer.onNext(true)
                observer.onCompleted()
            }else {
                print("failed:\(i)")
                let err = NSError.init(domain: "err", code: 1001, userInfo: nil)
                observer.onError(err)
            }
        }
        return Disposables.create()
    }.retry(3).shareReplay(1)
    return checkAccountO!
}

func fetchMails() -> Observable<[String]> {
    return checkAccount().flatMap({ (_) -> Observable<[String]> in
        return self.fetchO
    })
}

func fetchFolders() -> Observable<[String]> {
    return checkAccount().flatMap({ (_) -> Observable<[String]> in
        return self.fetchFolderO
    })
}

根据@Timofey Solonin的回答，我将可观察的fetchFoders和fetchMails从button.rx.tap更改为flatmap，如下所示，但仍然不知道如何使用retrywhen

    func fetchMails() -> Observable<[String]> {
    let rxtap = btn1.rx.tap
    return rxtap.flatMap { (_) -> Observable<[String]> in
        return self.checkAccount().flatMap({ (_) -> Observable<[String]> in
            return self.fetchO
        })
    }

}

func fetchFolders() -> Observable<[String]> {
    let rxtap = btn2.rx.tap
    return rxtap.flatMap { (_) -> Observable<[String]> in
        return self.checkAccount().flatMap({ (_) -> Observable<[String]> in
            return self.fetchFolderO
        })
    }
}

Answer 1

您可以使用 retryWhen 运算符。 flatMap 从 retryWhen 到 checkAccount 的错误流，如果 checkAccount 成功，您的操作将重试。

要从按钮启动流，您可以使用 button.rx.tap 和 flatMap 它。

例如，如果您想从 button.rx.tap 和 checkAcount() 多次调用 fetchMail()，如果 fetchMail () 出错了可以使用:

btn1.rx.tap.flatMapLatest {
    fetchMails().retryWhen{ errors in 
        errors.flatMapLatest{ _ in 
            checkAccount().retry() //or you can use retry(n) if you want to retry checkAccount limited amount of times.
            //fetchMails() will repeat if checkAccount() will return anything. Just keep in mind that retryWhen block is not going to be called if checkAccount() was successful.
        }
    }
}