GCD in iOS not updating my label - ios

Question

I am trying to update my custom label using GCD however all I am getting is the text I initialized the label with:
-(void)drawCardInfo{
__block NSString *cardString;
PPLinearLayoutLabelItem *cardDetails = [[PPLinearLayoutLabelItem alloc] initWithText:#"CREDIT CARD INFO" font:[PPFonts regular18] maxWidth:[LayoutValues getMaxWidthClipped]];
[cardDetails setPaddingTop:20];
[cardDetails setPaddingBottom:10];
[self.topContainerContent addObject:cardDetails];
PPLinearLayoutLabelItem *cardInfo = [[PPLinearLayoutLabelItem alloc] initWithText:#"Data" font:[PPFonts bold16] maxWidth:[LayoutValues getMaxWidthClipped]];
[cardInfo setPaddingTop:0];
[self.topContainerContent addObject:cardInfo];
LinearLayoutHorizontalLine *line1 = [[LinearLayoutHorizontalLine alloc] initWithMaxWidth:[LayoutValues getMaxWidthClipped]];
[self.topContainerContent addObject:line1];
dispatch_async( dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSOperationQueue *networkQueue = [[NSOperationQueue alloc] init];
networkQueue.maxConcurrentOperationCount = 5;
NSURL *url = [NSURL URLWithString:#"https://xxxxxxxxxxxxxxxxxx"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc]
initWithRequest:request];
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
NSString *string = [[NSString alloc] initWithData:responseObject encoding:NSUTF8StringEncoding];
if([string isEqualToString:#""]){
} else {
NSMutableDictionary *dict=[NSJSONSerialization JSONObjectWithData:[string dataUsingEncoding:NSUTF8StringEncoding] options:kNilOptions error:nil];
NSString *cardType = [dict objectForKey:#"credit_card_type"];
NSString *cardFinalFour = [dict objectForKey:#"credit_card_last_4"];
cardString = [NSString stringWithFormat:#"%# **** %#",cardType, cardFinalFour];
NSLog(#"%#",cardString);
}
dispatch_async(dispatch_get_main_queue(), ^{ [cardInfo setText:cardString]; });
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(#"%s: AFHTTPRequestOperation error: %#", __FUNCTION__, error);
}];
[networkQueue addOperation:operation];
});
}
I am successfully logging out the value proving that the network call works fine on a separate thread. Still my label is not being updated. How can I mitigate this?

Answer 1

Looks like you are trying to update the text for the label in a background thread. Updating UI elements on anywhere other than the main thread is not such a good idea since you never know when a asynchronous job will finish.
You can use the following ways to go about it:
Get the main thread and then update the text label
dispatch_async(dispatch_get_main_queue(), ^{
//Code here to which needs to update the UI in the UI thread goes here
});
Use dispatch_sync
Use NSOperations with dependancies (This will be the longest)