将 NSURLIsExcludedFromBackupKey 应用于 iPhone 上的服务器 URL 或目录 URL？

Posted 2023-03-07

【中文标题】将 NSURLIsExcludedFromBackupKey 应用于 iPhone 上的服务器 URL 或目录 URL？

【英文标题】：Apply NSURLIsExcludedFromBackupKey to Server URL or URL of Directory on iPhone?

【发布时间】：2013-11-12 22:09:05

【问题描述】：

由于我如何在 iPhone 上保存一些下载的文件，我正在与应用程序拒绝作斗争。

我已经实现了NSURLIsExcludedFromBackupKey，但我不清楚我是否正确地执行了它。我应该将NSURLIsExcludedFromBackupKey 应用于代表服务器上文件的 NSURL，还是以某种方式将其应用于 iPhone 上保存文件的目录？

这是我现在在应用被拒绝后创建的：

// Get / Create the File Directory on the iPhone 
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0]; // Get documents folder
NSString *dataPath = [documentsDirectory stringByAppendingPathComponent:@"MyDirectory"];

if (![[NSFileManager defaultManager] fileExistsAtPath:dataPath])
[[NSFileManager defaultManager] createDirectoryAtPath:dataPath withIntermediateDirectories:NO attributes:nil error:nil]; 

// Setup the NSURL where the PNG is located
NSURL *imageURL = [NSURL URLWithString:@"http://www.myserver.com/image.png"];

NSError *err = nil; // Exclude This Image from the iCloud backup system
BOOL excluded = [imageURL setResourceValue:[NSNumber numberWithBool:YES] forKey:NSURLIsExcludedFromBackupKey error:&err];

if (!excluded) 
        //NSLog(@"Failed to exclude from backup");
 else 
    //NSLog(@"Excluding from backup"); // this works...

// Create the UIImage
UIImage *image = [[UIImage alloc] initWithData:[NSData dataWithContentsOfURL:imageURL]];

// Data about the downloaded image
NSData *data1 = [NSData dataWithData:UIImagePNGRepresentation(image)];

if ([data1 writeToFile:pngFilePath atomically:YES] && [data1 writeToFile:pngFilePathRetina atomically:YES]) 
        // Saved to phone
 else         
        // Did not save to phone

【问题讨论】：

由于 ios 不备份远程文件，因此您可以确定 URL 必须是位于应用沙箱中的文件的文件 URL。

【参考方案1】：

这是我最终如何对其进行编码以使其获得批准的方式。这可能有点矫枉过正，但总比花一个月的时间去猜测究竟如何获得批准要好。

 // Get / Create the File Directory on the iPhone 
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0]; // Get documents folder
    NSString *dataPath = [documentsDirectory stringByAppendingPathComponent:@"MyDirectory"];

// if the directory does not yet exist on the phone, create it
    if (![[NSFileManager defaultManager] fileExistsAtPath:dataPath])
    [[NSFileManager defaultManager] createDirectoryAtPath:dataPath withIntermediateDirectories:NO attributes:nil error:nil]; 


    // Assign NSURLIsExcludedFromBackupKey to the directory at dataPath, so is does not backup to iCloud
    NSURL *directoryUrl = [NSURL fileURLWithPath:dataPath isDirectory:YES];
    NSError *err1 = nil;
    BOOL excluded1 = [directoryUrl
                         setResourceValue:[NSNumber numberWithBool:YES]
                         forKey:NSURLIsExcludedFromBackupKey
                         error:&err1];

    if (!excluded1) 
            //NSLog(@"Failed to exclude directory from backup");
     else 
            //NSLog(@"Excluding directory from backup");
    



    // Setup the NSURL where the PNG, which will be downloaded, is located 
    NSURL *imageURL = [NSURL URLWithString:@"http://www.myserver.com/image.png"];

    NSError *err2 = nil; // Exclude This Image from the iCloud backup system, Not sure if I need this or not…
    BOOL excluded2 = [imageURL setResourceValue:[NSNumber numberWithBool:YES] forKey:NSURLIsExcludedFromBackupKey error:&err2];

    if (!excluded2) 
        //NSLog(@"Failed to exclude from backup");
     else 
        //NSLog(@"Excluding from backup"); // this works...
    


   // Create the UIImage
    UIImage *image = [[UIImage alloc] initWithData:[NSData dataWithContentsOfURL:imageURL]];

    // Data about the downloaded image
    NSData *downloadedImageData = [NSData dataWithData:UIImagePNGRepresentation(image)];

    // Path for where we are going to save the image
    NSString *storePath = [NSString stringWithFormat:@"%@/myimage.png", dataPath]; 

    if ([downloadedImageData writeToFile:storePath atomically:YES]) 

  // the Image is saved to the phone

  // NSURL representing the image that is now saved on the phone          
  NSURL *imageOnPhone = [NSURL fileURLWithPath:storePath isDirectory:YES];

        // Exclude this image, which is now stored on the phone, from iCloud Backup
        NSError *err3 = nil;
        BOOL excluded3 = [imageOnPhone
                                  setResourceValue:[NSNumber numberWithBool:YES]
                                  forKey:NSURLIsExcludedFromBackupKey
                                  error:&err3];
            if (!excluded3) 
                //NSLog(@"Failed to exclude from backup (standard)");
             else 
                //NSLog(@"Excluding from backup (standard)");
            

     else         
            // Did not save to phone
    

【讨论】：

与其浪费时间和混乱检查目录是否存在，不如每次尝试创建它更快更简单

如果设置资源值失败，为了调试目的，注销它失败的错误会更有用

不要费心为您的远程 URL 设置NSURLIsExcludedFromBackupKey；它永远不会成功

您的代码会下载一个图像（同步，这很糟糕），从中创建一个UIImage，然后将其转换回PNG。几乎可以肯定，最好下载图像数据并直接存储，而无需尝试对 PNG 进行编码

[NSString stringWithFormat:@"%@/myimage.png", dataPath] — 不要这样做。请改用stringByAppendingPathComponent: 方法，如代码开头附近所示。更好的是，使用 URL 开头，而不是路径

【参考方案2】：

为了更简洁地回答你原来的问题：

您应该将NSURLIsExcludedFromBackupKey 应用于目的地。即您不想备份的文件或目录。

iPhone 不知道您的应用可能正在使用哪些远程文件，因此不可能尝试备份它们。更重要的是，如果您尝试在此类 URL 上设置 NSURLIsExcludedFromBackupKey，您很快就会发现由于 URL 不受支持而失败。