swift - 将文件从临时 url 复制到文档目录总是会抛出错误。 NSURLSessionDownloadTask

Question

我正在使用 NSURLSessionDownloadTask 下载文件，效果很好。当我将图像或视频文件放入临时目录时。但我需要将它移动到永久 URL 才能将其放入照片库。我正在使用 NSFileManager 的 copyItemAtURL: 但没有成功。它会抛出任何原因吗？也许文件类型与文档目录不兼容？

let directory : String = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0]


func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didFinishDownloadingToURL location: NSURL) {

    if let fileName = self.file.zOrigFileName {
        let destinationPath = self.directory.stringByAppendingString("/\(fileName)")

        if let destinationURL = NSURL(string: destinationPath) {

            let fileManager = NSFileManager.defaultManager()

            //IF file with same name exists delete it before copying new file
            if fileAlreadyExistsAtURL(destinationURL) {
                do {
                    try fileManager.removeItemAtURL(destinationURL)
                } catch {
                    print("Error Removing Item At \(destinationURL.path)")
                }
            }

            do {
                try fileManager.copyItemAtURL(location, toURL: destinationURL)
                self.saveURLToPhotosLibrary(destinationURL)
            } catch {
                //This is line always printing. my try statement always throwing.
                print("Error Copying Item from \(location.path) to \(destinationURL.path)")
            }
        }
    }
}

这是打印语句。为了安全起见，我将文档目录中的应用程序包 ID 替换为 $(AppId)

Error Copying Item from Optional("/private/var/mobile/Containers/Data/Application/E8D9C365-15D2-40BD-B0B5-A000BEDA9F00/Library/Caches/com.apple.nsurlsessiond/Downloads/$(AppID)/CFNetworkDownload_CK3G3Z.tmp") to Optional("/var/mobile/Containers/Data/Application/E8D9C365-15D2-40BD-B0B5-A000BEDA9F00/Documents/shortMovie.mov")

Answer 1

您使用了错误的 NSURL 初始值设定项。使用路径时，您需要使用 fileURLWithPath 初始值设定项。