使用UIImageWriteToSavedPhotosAlbum保存图片，但内存已满，如何抓取错误码

NSError *error = nil;

UIImageWriteToSavedPhotosAlbum(image, self, @selector(image:didFinishSavingWithError:contextInfo:), (__bridge void *)error);

- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo {
    if (error != nil) {
        // 保存图片出错，处理错误信息
        NSLog(@"保存图片出错，错误码：%ld，错误信息：%@", (long)error.code, error.localizedDescription);
    } else {
        // 保存图片成功
        NSLog(@"保存图片成功");
    }
}