Data is not loading in UITableView. What could be the issue? - iphone

Question

I have a UITableView in next segue when a button is pressed. The code that i have implemented in the implementation file is as follows. The view is shifting, but the data is not loading in the view.
What could be the problem?
- (void)viewDidLoad
{
[super viewDidLoad];
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSData* data = [NSData dataWithContentsOfURL:
[NSURL URLWithString: #"https://api.twitter.com/1/statuses/public_timeline.json"]];
NSError* error;
tweets = [NSJSONSerialization JSONObjectWithData:data
options:kNilOptions
error:&error];
dispatch_async(dispatch_get_main_queue(), ^{
[self.tableView reloadData];
});
});
// Uncomment the following line to preserve selection between presentations.
// self.clearsSelectionOnViewWillAppear = NO;
// Uncomment the following line to display an Edit button in the navigation bar for this view controller.
// self.navigationItem.rightBarButtonItem = self.editButtonItem;
}
- (void)viewDidUnload
{
[super viewDidUnload];
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
// Return the number of sections.
return 0;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return tweets.count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"TweetCell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
NSDictionary *tweet = [tweets objectAtIndex:indexPath.row];
NSString *text = [tweet objectForKey:#"text"];
NSString *name = [[tweet objectForKey:#"user"] objectForKey:#"name"];
cell.textLabel.text = text;
cell.detailTextLabel.text = [NSString stringWithFormat:#"by %#", name];
return cell;
}

Answer 1

(NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
// Return the number of sections.
return 0;
}
Don't you need at least 1 section?

Answer 2

You should use breakpoints in the debugger to break on the numberOfRowsInSection method and cellForRowAtIndexPath to verify that your data is being parsed and handled correctly. If you're unfamiliar with breakpoints now is a good chance to get to know them - they are invaluable in debugging and resolving problems.
As a general note, you probably shouldn't be using dataWithContentsOfURL to do your networking. It's not really designed for that usage. NSURLConnection is a much better option, which will give you far more flexibility.

Answer 3

dyspatch_async
is named is as because it's asynchronous. You seem to be thinking that the second call to it is executed after the first call - but no. They're executes parallel, and because the URL operation is slower, the table view's update occurs when there's no data yet.
Solution: put the reloadData call in the same block as the URL operation - you don't need two separate calls to dispatch_async.
Also, you return 0 from
numberOfSectionsInTableView:
so the table doesn't even look for data. Return 1.