objective c - GCD wait until all task in queue are finished -

in app got photo upload function , want main queue wait until photo upload done. here's code :

    dispatch_group_t groupe = dispatch_group_create(); dispatch_queue_t queue = dispatch_queue_create("com.freesale.chlebta.photouplaod", 0);  dispatch_group_async(groupe, queue, ^{      //upload photo in same array annonce     //++++++++++++++++++++++++++++++++++++++     if(!_annonce)         [kvnprogress updatestatus:@"جاري رفع الصور"];      __block nsinteger numberphototoupload = _photoarray.count - 1;      (int = 1; < _photoarray.count; i++) {         //check if image asset upload else decrement photo numver because it's uploaded         if ( [[_photoarray objectatindex:i] iskindofclass:[alasset class]]){             alasset *asset = [_photoarray objectatindex:i];              nsdata *imagedata = uiimagejpegrepresentation([uiimage imagewithcgimage:[[asset defaultrepresentation] fullresolutionimage]], 0.6);              pffile *imagefile = [pffile filewithname:@"image.png" data:imagedata];             [imagefile saveinbackgroundwithblock:^(bool succeeded, nserror *error) {                 if (succeeded)                     [annonce adduniqueobject:imagefile forkey:@"photo"];                 else                     nslog(@"error image upload \n image :%i \n error:  %@",i, error);                      numberphototoupload --;             }];         } else             numberphototoupload --;      }  });  //wait until photo upload finished  dispatch_group_wait(groupe, dispatch_time_forever);  // other operation  

but didn't worked, program continue execution without waiting photo upload finished.

because using saveinbackgroundwithblock: method in block, right?

https://parse.com/docs/osx/api/classes/pffile.html#//api/name/saveinbackgroundwithblock:

saves file asynchronously , executes given block. 

you need call dispatch_group_enter , dispatch_group_leave method following if want wait background-processed block.

dispatch_group_enter(groupe); [imagefile saveinbackgroundwithblock:^(bool succeeded, nserror *error) {     dispatch_group_leave(groupe);      ...  }]; 

by way,

i want main queue wait until photo upload done

it's not idea. don't block main thread (the main queue).

app programming guide ios - performance tips - move work off main thread

be sure limit type of work on main thread of app. main thread app handles touch events , other user input. ensure app responsive user, should never use main thread perform long-running or potentially unbounded tasks, such tasks access network.