将远程文件复制到临时ios文件时出现错误：文件已存在

Question

我正在从URL下载Excel，然后尝试将Excel文件复制到本地临时文件中。临时文件路径每次都是唯一的，因为临时目录提供了基于UUID字符串的唯一路径。例如：第一次的路径是：文件：///private/var/mobile/Containers/Data/Application/FCA022DB-3B65-499E-9F91-190E307285B0/tmp/WindData.csv。第二次路径不同：/ private / var / mobile /容器/数据/应用程序/6CB02402-837D-4952-8C56-58572705B0AD/tmp/WindData.csv。

但是即使路径是唯一的，第二次出现错误“文件存在”。因此，通过FileManager.default.fileExists检查该文件是否存在，如果发现为true，则删除文件路径。此检查返回的错误就好像文件不存在一样，但是在下一行中，当我尝试将目标文件复制到目标Url时（因为它在上一行中不存在），它给出了错误消息：“错误：错误域= NSCocoaErrorDomain代码= 516”“ CFNetworkDownload_oHoanb.tmp“无法复制到” tmp“，因为已经存在具有相同名称的项目。” UserInfo = {NSSourceFilePathErrorKey = / private / var / mobile / Containers /数据/应用程序/DB863D34-3F66-45C8-B129-76DB6FC61D0E/tmp/CFNetworkDownload_oHoanb.tmp，NSUserStringVariant =（复制），NSDestinationFilePath = / private / var / mobile / Containers / Data / Application / DB863D34-3F66-45C8-B129-76DB6FC61D0E / tmp / WindData.csv，NSFilePath = / private / var / mobile / Containers / Data / Application / DB863D34- 3F66-45C8-B129-76DB6FC61D0E / tmp / CFNetworkDownload_oHoanb.tmp，NSUnderlyingError = 0x2801e93b0 {Error Domain = NSPOSIXErrorDomain Code = 17“文件存在”}}“]

如何解决此问题？

 let datadownloadTask = URLSession.shared.downloadTask(with: vendorURL!, completionHandler: { (responseUrl, response, error) in
        do {
            if let tempUrl = responseUrl {
                if let statusCode = (response as? HTTPURLResponse)?.statusCode {
                    print("Successfully downloaded. Status code: \(statusCode)")
                }

                do {
                    let targetUrl = self.copyResourcetoTempFile(sourceUrl: tempUrl, resourceName: "WindData", fileExtension: "csv")
                    if let destUrl = targetUrl {
                        let data = try String(contentsOfFile: destUrl.absoluteString!, encoding: .utf8)
                        let avg = self.parseCsv(data: data)
                        self.avg = avg
                    }

                } catch (let writeError) {
                    print("Error creating a file \(tempUrl) : \(writeError)")
                }

                completion(self.avg)
            }
        } catch {
            print("error: \(error.localizedDescription)")
        }
    })
    datadownloadTask.resume()
}

public func copyResourcetoTempFile(sourceUrl: URL, resourceName: String, fileExtension: String) -> NSURL?
{
    let tempDirectoryURL = NSURL.fileURL(withPath: NSTemporaryDirectory(), isDirectory: true)
    let targetUrl = tempDirectoryURL.appendingPathComponent(resourceName).appendingPathExtension(fileExtension)
    do {
        if FileManager.default.fileExists(atPath: targetUrl.absoluteString) {
           try FileManager.default.removeItem(at: targetUrl)
        }
        try FileManager.default.copyItem(at: sourceUrl, to: targetUrl)
        return targetUrl as NSURL
    } catch let error {
        NSLog("Error: \(error)")
    }
    return nil
}

Answer 1

您犯了一个非常常见的错误：

路径是path，而不是absoluteStringif FileManager.default.fileExists(atPath: targetUrl.path) {

并且没有理由在Swift中使用NSURL
let tempDirectoryURL = URL(fileURLWithPath: NSTemporaryDirectory(), isDirectory: true)