The iOS SDK has an upload function that can be called directly,

    NSString token = @"从服务端SDK获取";
    QNUploadManager *upManager = [[QNUploadManager alloc] init];
    NSData *data = [@"Hello, World!" dataUsingEncoding : NSUTF8StringEncoding];
    [upManager putData:data key:@"hello" token:token
        complete: ^(QNResponseInfo *info, NSString *key, NSDictionary *resp) {
        NSLog(@"%@", info);
        NSLog(@"%@", resp);
    } option:nil];

If you are talking about letting your backend upload to your server, then you can also let your backend server access the server's SDK:

http://developer.qiniu.com/docs/v6/index.html