exportVideoToRoll.m

@import Photos;
@import AVKit;
[PHPhotoLibrary.sharedPhotoLibrary performChanges:^{

     NSURL *url = [NSURL fileURLWithPath:[FileUtil filePath:fileName]];
     [PHAssetChangeRequest creationRequestForAssetFromVideoAtFileURL:url];

         } completionHandler:^(BOOL success, NSError * _Nullable error) {
               if (error) {
                    NSLog(@"Error : %@", error);
                }

                if (success) {
                    NSLog(@"Finished updating assets.");
                }
     }];