ios - 在 downloadTask 完成后执行 segue

Question

我正在构建一个应用程序，一旦它连接到特定的本地网络，它就会显示一个事件指示器，然后开始下载图像的 zip 文件，一旦图像下载完毕，它就会解压缩文件，停止指示器，然后执行 segue 以下一个 View Controller 。我拥有所有功能，但不知道如何查看功能何时完成。我的 Donloader 类如下所示:

class Downloader {

    let documentsUrl: URL =  FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first as URL!

    required init() {

        self.load()
    }

    func load() {

        // Create destination URL
        let destinationFileUrl = documentsUrl.appendingPathComponent("Images.zip")

        //Create URL to the source file you want to download
        let fileURL = URL(string: "http://127.0.0.1:4567/download")//FIXME for production

        //Create Session
        let sessionConfig = URLSessionConfiguration.default
        let session = URLSession(configuration: sessionConfig)
        let request = URLRequest(url:fileURL!)

        let task = session.downloadTask(with: request) { (tempLocalUrl, response, error) in

            if let tempLocalUrl = tempLocalUrl, error == nil {
                // Success
                if let statusCode = (response as? HTTPURLResponse)?.statusCode {
                    print("Successfully downloaded. Status code: \(statusCode)")
                }

                do {

                    try FileManager.default.copyItem(at: tempLocalUrl, to: destinationFileUrl)
                } catch (let writeError) {

                    print("Error creating a file \(destinationFileUrl) : \(writeError)")
                }

            } else {

                print("Error took place while downloading a file. Error description: %@", (error?.localizedDescription)! as String);
            }
        }
        task.resume()
    }
}

我的 File 类中的解压缩函数如下所示:

func unZip() {


    let zipFileURL = documentsURL?.appendingPathComponent("Images.zip")

    SSZipArchive.unzipFile(atPath: (zipFileURL?.path)!, toDestination: (documentsURL?.path)!)

    var directoryContents = [URL]()

    do {
        // Get the directory contents urls (including subfolders urls)
        directoryContents = try fileManager.contentsOfDirectory(at: documentsURL!, includingPropertiesForKeys: nil, options: [])
    } catch let error as NSError {

        print(error.localizedDescription)
    }

    let pngFiles = directoryContents.filter{ $0.pathExtension == "png" }//FIXME change file types if needed

    imageNamesArray = pngFiles.map{ $0.deletingPathExtension().lastPathComponent }
}

我看过闭包，但不明白如何从类外部或另一个 ViewController 调用它们。任何帮助都会非常感谢。

Answer 1

添加一个没有返回值的完成处理程序非常简单。将 load 方法更改为

func load(finished: @escaping ()->()) 

任务结束时调用finished()

  let task = session.downloadTask(with: request) { ...

     finished()
  }

并以这种方式调用load()

load() {
  // task has finished
}

但是对于完成处理程序，您应该删除 required init 并分别调用 init 和 load。