Perform action after findObjectsInBackgroundWithBlock completed in for loop - ios

Question

I have such construction in my code:
for (METMeetingEntity *e in self.meetingList) {
PFQuery *query = [PFUser query];
//some query constraints, depending on METMeetingEntity
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error)
{
// some query actions
NSArray *sortDescriptors = #[[NSSortDescriptor sortDescriptorWithKey:#"date" ascending:YES]];
self.meetingList = [NSMutableArray arrayWithArray:[self.meetingList sortedArrayUsingDescriptors:sortDescriptors]];
self.meetingList = [self dateCleanup:self.meetingList];
}];
How can I perform action - reload my table view after all the findObjectsInBackground are completed

Answer 1

One possible solution would be to keep a count. When the number matches the original count, you know you are done.
NSUInteger count = self.meetingList.count;
for (METMeetingEntity *e in self.meetingList) {
PFQuery *query = [PFUser query];
//some query constraints, depending on METMeetingEntity
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
// some query actions
NSArray *sortDescriptors = #[[NSSortDescriptor sortDescriptorWithKey:#"date" ascending:YES]];
self.meetingList = [NSMutableArray arrayWithArray:[self.meetingList sortedArrayUsingDescriptors:sortDescriptors]];
self.meetingList = [self dateCleanup:self.meetingList];
count--;
if (count == 0) {
dispatch_async(dispatch_get_main_queue(), ^{
// reload table or whatever needs to be done
});
}
}];
}

Answer 2

I think you don't need calling dispatch_async. All the blocks in Parse run in the main thread. In Parse doc you can read:
Both findObjectsInBackgroundWithBlock: and
findObjectsInBackgroundWithTarget:selector: work similarly in that
they assure the network request is done without blocking, and run the
block/callback in the main thread.
This is an example of a query for a UICollectionView:
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if(!error) {
listaFiguras = [objects mutableCopy];
[_collectionView reloadData];
} else {
NSLog(#"Something wrong. No Data.");
}
}];