AlamoFire 的使用 (下载队列，断点续传)

/// Creates a `DataRequest` using the default `SessionManager` to retrieve the contents of the specified `url`,
/// `method`, `parameters`, `encoding` and `headers`.
///
/// - parameter url:        The URL.
/// - parameter method:     The HTTP method. `.get` by default.
/// - parameter parameters: The parameters. `nil` by default.
/// - parameter encoding:   The parameter encoding. `URLEncoding.default` by default.
/// - parameter headers:    The HTTP headers. `nil` by default.
///
/// - returns: The created `DataRequest`.
public func request(_ url: URLConvertible, method: Alamofire.HTTPMethod = default, parameters: Parameters? = default, encoding: ParameterEncoding = default, headers: HTTPHeaders? = default) -> Alamofire.DataRequest

/// Creates a `DataRequest` using the default `SessionManager` to retrieve the contents of a URL based on the
/// specified `urlRequest`.
///
/// - parameter urlRequest: The URL request
///
/// - returns: The created `DataRequest`.
public func request(_ urlRequest: URLRequestConvertible) -> Alamofire.DataRequest

let req : URLRequest = URLRequest(url: URL(fileURLWithPath: "32"), cachePolicy: .useProtocolCachePolicy, timeoutInterval: 10)

        // 第一种方法调用，后面参数直接用default
        Alamofire.request(URL(fileURLWithPath: "32"))

        // 第二中调用，使传入request
        Alamofire.request(req)
        let semaphore = DispatchSemaphore(value: 0)

let networkManager : SessionManager = {
        let config : URLSessionConfiguration = URLSessionConfiguration.default
        config.timeoutIntervalForRequest = 10
        let manager = Alamofire.SessionManager.init(configuration: config)
        return manager
    }()

Alamofire.download("http://clips.vorwaerts-gmbh.de/big_buck_bunny.mp4", method: .get, parameters: nil, encoding: URLEncoding.default, headers: nil) { (url, response) -> (destinationURL: URL, options: DownloadRequest.DownloadOptions) in
            return (URL(fileURLWithPath: String(describing : NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, false)[0]+"123.mp4")), [.createIntermediateDirectories, .removePreviousFile])
            }.responseJSON { (response) in

                switch response.result {

                case .success:
                    print("success")
                case .failure:
                    //意外中断后在此处处理下载完成的部分
                    self.tmpData = response.resumeData

                default:
                    print("failed")
                }

        }

/// Creates a `DownloadRequest` using the default `SessionManager` from the `resumeData` produced from a
/// previous request cancellation to retrieve the contents of the original request and save them to the `destination`.
///
/// If `destination` is not specified, the contents will remain in the temporary location determined by the
/// underlying URL session.
///
/// On the latest release of all the Apple platforms (iOS 10, macOS 10.12, tvOS 10, watchOS 3), `resumeData` is broken
/// on background URL session configurations. There's an underlying bug in the `resumeData` generation logic where the
/// data is written incorrectly and will always fail to resume the download. For more information about the bug and
/// possible workarounds, please refer to the following Stack Overflow post:
///
///    - http://stackoverflow.com/a/39347461/1342462
///
/// - parameter resumeData:  The resume data. This is an opaque data blob produced by `URLSessionDownloadTask`
///                          when a task is cancelled. See `URLSession -downloadTask(withResumeData:)` for additional
///                          information.
/// - parameter destination: The closure used to determine the destination of the downloaded file. `nil` by default.
///
/// - returns: The created `DownloadRequest`.
public func download(resumingWith resumeData: Data, to destination: Alamofire.DownloadRequest.DownloadFileDestination? = default) -> Alamofire.DownloadRequest

Alamofire.download(resumingWith: tmpData!)

let op : BlockOperation = BlockOperation { [weak self] in
            Alamofire.download("http://clips.vorwaerts-gmbh.de/big_buck_bunny.mp4", method: .get, parameters: nil, encoding: URLEncoding.default, headers: nil) { (url, response) -> (destinationURL: URL, options: DownloadRequest.DownloadOptions) in
                return (URL(fileURLWithPath: String(describing : NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, false)[0]+"123.mp4")), [.createIntermediateDirectories, .removePreviousFile])
                }.downloadProgress { [weak self] (pro) in
                    let percent = Float(pro.completedUnitCount) / Float(pro.totalUnitCount)
                    if count == 0 {

                        self?.downLoadLabel.snp.remakeConstraints { (make) in
                            make.width.equalTo(300 * percent)
                            make.height.equalTo(30)
                            make.top.equalTo((self?.stopButton.snp.bottom)!).offset(30)
                            make.left.equalToSuperview().offset(30)
                        }
                    } else {
                        self?.downLoadLabel2.snp.remakeConstraints { (make) in
                            make.width.equalTo(300 * percent)
                            make.height.equalTo(30)
                            make.top.equalTo((self?.downLoadLabel.snp.bottom)!).offset(30)
                            make.left.equalToSuperview().offset(30)
                        }
                    }
                }.responseJSON { (response) in

                    switch response.result {

                    case .success:
                        print("success")
                    case .failure:
                        self?.tmpData = response.resumeData

                    default:
                        print("failed")
                    }

            }
        }

        queue.addOperation(op)

let queue : OperationQueue = {
        let que : OperationQueue = OperationQueue()
        que.maxConcurrentOperationCount = 1
        return que
    }()