如何防止文件备份到iCloud和iTunes

How do I prevent files from being backed up to iCloud and iTunes?

Q: My app has a number of files that need to be stored on the device permanently for my app to function properly offline. However, those files do not contain user data and don’t need to be backed up. How can I prevent them from being backed up?

Starting in iOS 5.1, apps can use either NSURLIsExcludedFromBackupKey or kCFURLIsExcludedFromBackupKey file system properties to exclude files and directories from backups. Apps that need to exclude a large number of files can exclude them by creating their own sub-directory and marking that directory as excluded. Apps should create their own directories for exclusion, rather than excluding the system defined directories. Either of these APIs is preferred over the older, deprecated approach of directly setting an extended attribute. All apps running on iOS 5.1 and later should use these APIs to exclude data from backups.

- (BOOL)addSkipBackupAttributeToItemAtPath:(NSString *) filePathString
{
    NSURL* URL= [NSURL fileURLWithPath: filePathString];
    assert([[NSFileManager defaultManager] fileExistsAtPath: [URL path]]);

    NSError *error = nil;
    BOOL success = [URL setResourceValue: [NSNumber numberWithBool: YES]
                                  forKey: NSURLIsExcludedFromBackupKey error: &error];
    if(!success){
        NSLog(@"Error excluding %@ from backup %@", [URL lastPathComponent], error);
    }
    return success;
}