RequestRetrier Alamofire鎖不起作用

Question

我正在用Alamofire實現RequestRetrier，以刷新給定用戶的accessToken。

func should(_ manager: SessionManager, retry request: Request, with error: Error, completion: @escaping RequestRetryCompletion) {
    lock.lock() ; defer { lock.unlock() }

    if let response = request.task?.response as? HTTPURLResponse, response.statusCode == 401 {
        requestsToRetry.append(completion)

        if !isRefreshing {
            refreshToken(completion: { [weak self] succeded, accessToken in

                guard let strongSelf = self else { return }

                strongSelf.lock.lock() ; defer { strongSelf.lock.unlock() }

                strongSelf.requestsToRetry.forEach{ $0(succeded, 0.0) }
                strongSelf.requestsToRetry.removeAll()
            })
        }
    } else {
        completion(false, 0.0)
    }
}

當strongSelf.lock.lock() ; defer { strongSelf.lock.unlock() } strongSelf.lock.lock() ; defer { strongSelf.lock.unlock() }被稱為它不會繼續執行，因此存在無限循環。 我嘗試檢查strongSelf.lock.try()的結果並返回false。

當我使用錯誤的密碼登錄時會發生這種情況，因此服務器返回401。

這是我的refreshToken代碼

guard !isRefreshing else { return }

// ... Get user ... //
if let user = user {

    isRefreshing = true
    signIn(user: userDTO)
        .subscribe(onNext: { [weak self] userSession in
            guard let strongSelf = self else { return }
            // ... Save accessToken ... //
            completion(true, userSession.accessToken)
            strongSelf.isRefreshing = false
        }, onError: { [weak self] error in
            guard let strongSelf = self else { return }
            // ... Log out user ... //
            completion(false, nil)
            strongSelf.isRefreshing = false
        })
        .disposed(by: bag)
} else {
        completion(false, nil)
}

Answer 1

如Github問題https://github.com/Alamofire/Alamofire/issues/2544所示，我可以通過以下方法解決此問題：

private let lock = NSLock()

至

private let lock = NSRecursiveLock()

它們之間的區別在於，如果同一線程嘗試鎖定，則可以解鎖遞歸鎖定。