swift, alamofire 取消之前的请求

Question

我有一个 NetworkRequest 类，我所有的 alamofire 请求都在这里:

    class NetworkRequest {
        static let request = NetworkRequest()

        var currentRequest: Alamofire.Request?

        let dataManager = DataManager()
        let networkManager = NetworkReachabilityManager()
        let priority = DISPATCH_QUEUE_PRIORITY_DEFAULT

        func downloadData<T: Film>(slug: String, provider: String, section: String, dynamic: String, anyClass: T, completion: ([T]?) -> Void ) {
            var token: String = ""

            if LOGGED_IN == true {
                token = "\(NSUserDefaults.standardUserDefaults().valueForKey(TOKEN)!)"
            }

            let headers = [
                "Access": "application/json",
                "Authorization": "Bearer \(token)"
            ]

            let dataUrl = "\(BASE_URL)\(slug)\(provider)\(section)\(dynamic)"
            print(headers)
            print(dataUrl)

            if networkManager!.isReachable {

                currentRequest?.cancel()

                dispatch_async(dispatch_get_global_queue(priority, 0)) {

                    if let url = NSURL(string: dataUrl) {
                        let request = Alamofire.request(.GET, url, headers: headers)

                        request.validate().responseJSON { response in
                            switch response.result {
                            case .Success:
                                if let data = response.result.value as! [String: AnyObject]! {
                                    let receivedData = self.dataManager.parseDataToFilms(data, someClass: anyClass)
                                    completion(receivedData)
                                }

                            case .Failure(let error):
                                print("Alamofire error: \(error)")

                                if error.code == 1001 {
                                    self.goToNoConnectionVC()
                                }

                                print("canceled")
                            }

                        }
                    }
                }
            } else {
                goToNoConnectionVC()
            }
        }
}

我需要取消之前的下载数据请求，当新请求开始时，尝试使用 currentRequest?.cancel() 取消，但没有帮助。

已经尝试使用 NSOperationsBlock 取消操作，但它不会取消当前操作。

我现在阻止了 UI，这样用户就无法发送另一个请求。但这是不正确的，稍后会导致一些错误...

请帮忙

Answer 1

现在 Alamofire 4 Alamofire.Manager.sharedInstance.session 不可用，你应该使用 this解决方案:

let sessionManager = Alamofire.SessionManager.default 
sessionManager.session.getTasksWithCompletionHandler { dataTasks, uploadTasks, downloadTasks in 
dataTasks.forEach { $0.cancel() } 
uploadTasks.forEach { $0.cancel() } 
downloadTasks.forEach { $0.cancel() } 
}

如果你想取消(暂停、恢复)一个特定的请求，你可以在你的 .forEach block 中检查请求 url，如下所示:

dataTasks.forEach {
                if ($0.originalRequest?.url?.absoluteString == url) {
                    $0.cancel()
                }
            }