func thumbnailOfVideo(path : String)-> UIImage {
  do {
    let asset = AVURLAsset(url: URL(fileURLWithPath: path), options: nil)
    let imgGenerator = AVAssetImageGenerator(asset: asset)
    imgGenerator.appliesPreferredTrackTransform = true
    let cgImage = try imgGenerator.copyCGImage(at: CMTimeMakeWithSeconds(1, 24), actualTime: nil)
    let uiImage = UIImage(cgImage: cgImage)
    return uiImage
  } catch {
    return UIImage(named: "default_figure")!
  }
}

#import <AssetsLibrary/AssetsLibrary.h>
- (void)saveVideoIntoAlbum {
  NSString *fileDirectory = 
  NSFileManager *fileManager = [NSFileManager defaultManager];
  NSArray *fileArray = [fileManager contentsOfDirectoryAtPath:fileDirectory error:nil];
  NSString *filePath = [fileDirectory stringByAppendingPathComponent:[fileArray lastObject]];
  NSURL *fileUrl = [NSURL fileURLWithPath:filePath];
  
  NSLog(@"fileUrl = %@", fileUrl);
  ALAssetsLibrary *assetslibrary = [[ALAssetsLibrary alloc] init];
  
  if ([assetslibrary videoAtPathIsCompatibleWithSavedPhotosAlbum:fileUrl]) {
    [assetslibrary writeVideoAtPathToSavedPhotosAlbum:fileUrl completionBlock:^(NSURL *assetURL, NSError *error) {
      NSLog(@"%@-----%@", assetURL, error);
    }];
  } else {
    
  }
}