Question

I have created a class to generate tickets and when the ticket is generated I want to show it in the table view one by one.
I have created a protocol for that class and once the ticket is prepared I send a message to its delegate which is tableView to reload the table view.
when the reload method is called on the tableView - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section is being called every time a new ticket is generated but the
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath is not being called every time the ticket is generated but once all the tickets are generated it is being called

below is the code

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    if (self.ticketGenerator == nil) {
        return 0;
    }
    else{
        return self.ticketGenerator.ticketNumbers.count;
    }
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"Cell";
    HSEticketView *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[HSEticketView alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
        [cell Tickets:[self.ticketGenerator.ticketNumbers objectAtIndex:indexPath.row]];
    }

    // Configure the cell...

    return cell;
}

//to increase the height of the cell

- (CGFloat)tableView:(UITableView *)aTableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    return 135;
}

-(void)background
{
    [self.ticketGenerator GenerateNoOfTickets:[self.enteredNo.text intValue]:self];
}


- (IBAction)done:(id)sender {
    [self.enteredNo resignFirstResponder];
    self.enteredNo.hidden = YES;
    self.label.hidden = YES;
    self.button.hidden = YES;
    self.tableView.hidden = NO;

    [self performSelectorInBackground:@selector(background) withObject:nil];
        NSLog(@"dgf");

}

#pragma ticketGenrate delgate methods

-(void)generationOfTicketCompleated
{
    [self.tableView reloadData];


}

Answer 1

All changes to the UI must be done on the main thread. If you execute

[self.ticketGenerator GenerateNoOfTickets:...]

on a background thread and (as I assume) that functions calls

[tableView insertRowsAtIndexPaths:...]

that will not work, because insertRowsAtIndexPaths must be called on the main thread.

If you want to update the table view from a background thread, you can for example do

dispatch_async(dispatch_get_main_queue(), ^{
    add item to data source array ...;
    [tableView insertRowsAtIndexPaths:...];
});