TableViewController's Table View not displaying until the data is loaded - iphone

Question

I'm facing a strange issue. I have a method which populates an array with some data (fetchData) (quite a lot actually and it's a bit slow). I'm using the array to build the rows of the table.
I've tried calling fetchData in a number of places in my code, at various times in the construction of the view and I always seem to get the following: a black screen which is shown until the data from the array is loaded. I've called fetchData from the following:
(void)viewDidLoad;
(void)viewWillAppear:(BOOL)animated;
(void)viewDidAppear:(BOOL)animated;
Since I'm using a navigation view controller, having the app appear to hang is pretty bad looking since it gets stuck on a black screen. What I was hoping my code would achieve was displaying an empty table, with a progress indicator until the data is loaded - then refresh. Unfortunately I'm not getting this far since the view isn't being loaded no matter where I call fetchData.
Help appreciated!
P.S. To get around this problem I even tried using a TTTableViewController, but the Loading view is never displayed. Typical. sigh

Answer 1

Your load method must be blocking the UI. You should move it to another thread and let the data load there. You can instantiate the thread in viewDidLoad.
This is a skeleton code for that you need to (using GCD)
dispatch_queue_t downloadQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
dispatch_async(downloadQueue, ^{
... Move all the loading part here.
dispatch_async(dispatch_get_main_queue(),^{
... Do all the UI updates, mostly, [tableView reloadData];
})
})

Answer 2

It possible that you could add a timer to delay the call somewhere in your viewDidAppear method. For example:
- (void)viewDidAppear:(BOOL)animated {
[NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:#selector(fetchData) userInfo:nil repeats:NO];
}
This will give your app time to load the UI and start your loading screen, then start fetching the data later. You can also try fetching the data in a background thread if you would prefer to go that route

Answer 3

I was having the same issue with a table view not loading initially, but it worked n another .m file I had. Here is the one that worked:
add this to your viewDidLoad:
NSError *error = nil;
if (![[self fetchedResultsController] performFetch:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
and this to the implementation block:
#pragma mark -
#pragma mark Fetched results controller
- (NSFetchedResultsController *)fetchedResultsController {
if (fetchedResultsController == nil) {
// Create the fetch request for the entity.
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
// Edit the entity name as appropriate.
NSEntityDescription *entity = [NSEntityDescription entityForName:#"OMFrackinG" inManagedObjectContext:managedObjectContext];
[fetchRequest setEntity:entity];
// grouping and sorting optional
//NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"country" ascending:YES];
NSSortDescriptor *sortDescriptor1 = [[NSSortDescriptor alloc] initWithKey:#"state" ascending:YES];// was name
NSSortDescriptor *sortDescriptor2 = [[NSSortDescriptor alloc] initWithKey:#"name" ascending:YES];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor1,sortDescriptor2, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
propriate.
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:#"state" cacheName:nil];//#"state"
aFetchedResultsController.delegate = self;
self.fetchedResultsController = aFetchedResultsController;
[aFetchedResultsController release];
[fetchRequest release];
[sortDescriptor1 release];
[sortDescriptor2 release];
[sortDescriptors release];
}
return fetchedResultsController;
}