NSNotificationCenter Thread Issue

I'm working on a app that uses the UITableView:

I will fetch data from a web server, parse it, and display information in the table.

Code looks like the following (before):

-(void)fetchAndParse

{

    // Fetch and Parse

    

    [[NSNotificationCenter defaultCenter] postNotificationName:kDataRetrieved object:nil userInfo:userInfo];

}

- (void)dataRetrivalSucceeded:(NSNotification *)notification

{

    // Save data

    [myTable reloadData];

}

It was working fine until I decided to put parsing into a separate thread (using NSOperation), data sometimes shows up and sometimes doesn't. The UITableView will load data as usual, or remain blank until I drag it.

Code after:

-(void)fetch

{

    // Fetch

    queue = [NSOperationQueue new];

    NSInvocationOperation *summaryOperation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(parseXml:) object:data];

    [queue addOperation:parseOperation];

    [summaryOperation release];

}

-(void)parseXml

{

    // Parse

    [[NSNotificationCenter defaultCenter] postNotificationName:kDataRetrieved object:nil userInfo:userInfo];

}

- (void)dataRetrivalSucceeded:(NSNotification *)notification

{

    // Save data

    [myTable reloadData];

}

And that's when I found out the notification is delivered in the thread in which the notification was posted (Link).

In a multithreaded application, notifications are always delivered in the thread in which the notification was posted, which may not be the same thread in which an observer registered itself.

So what I did to make it work is the following:

-(void)fetch

{

    // Fetch

    queue = [NSOperationQueue new];

    NSInvocationOperation *summaryOperation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(parseXml:) object:data];

    [queue addOperation:parseOperation];

    [summaryOperation release];

}

-(void)parseXml

{

    // Parse

    [[NSNotificationCenter defaultCenter] postNotificationName:kDataRetrieved object:nil userInfo:userInfo];

}

- (void)dataRetrivalSucceeded:(NSNotification *)notification

{

    [self performSelectorOnMainThread:@selector(updateTable:) withObject:notification waitUntilDone:NO];

}

- (void)updateTable:(NSNotification *)notification

{

    // Save data

    [myTable reloadData];

}

The reason data shows after I dragged it is because it calls [myTable reloadData]; on main thread, while I wasn't.