iOS Objective-C NSURLSession not updating UI / property - ios

Question

I'm having some trouble updating my UI in my Objective-C iOS app.
Im calling my function fetchData in the viewDidLoad section of my ViewController.
The NSURLSession succesfully fetches the data however I am unable to update the titleText property in my UI even though its on the main queue.
I can update property in the viewDidLoad method, So I have a feeling this is something to do with the asynchronous request.
However I have tried multiple ways with no luck so any help would be much appreciated.
- (void) fetchData
{
NSString *strURl = #"www.url.com";
NSLog(#"%#",strURl);
NSURLSession *session = [NSURLSession sharedSession];
[[session dataTaskWithURL:[NSURL URLWithString:strURl]
completionHandler:^(NSData *data,
NSURLResponse *response,
NSError *error) {
if (data == nil) {
UIAlertController *alertController = [UIAlertController alertControllerWithTitle:NSLocalizedString(#"error", nil)message:NO_CONNECTION_TEXT preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction* ok = [UIAlertAction actionWithTitle:NSLocalizedString(#"ok", nil) style:UIAlertActionStyleDefault handler:nil];
[alertController addAction:ok];
[self presentViewController:alertController animated:YES completion:nil];
return ;
}
else
{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
if (!parsedDetails){
parsedDetails = [[NSMutableArray alloc]init];
}
parsedDetails = [provider parseJSON:data into:parsedDetails withResponse:response];
NSLog(#"%#",parsedDetails);
dispatch_async(dispatch_get_main_queue(), ^{
NSLog(#"%#",parsedDetails);
NSLog(#"%#",[parsedDetails valueForKey:#"title"]);
self.titleText = [parsedDetails valueForKey:#"title"];
});
});
}
}] resume];
}

Answer 1

Part 1: Determining the title
parsedDetails is a NSMutableArray in your code.
Then you are using the KVC (Key-Value Coding) method valueForKey on that array.
But that does return a new array. What happens there: the value of the title property for each element in the original array (parsedDetails) is inserted as a new element in a new array which is finally returned as array.
Due to your comment above:
NSLog(#"%#",[parsedDetails valueForKey:#"title"]);
gives the return value (an array with one string):
("About")
But what you actually want is the title element of the first entry, so rather something like this:
Detail *detail = parsedDetails.firstObject;
if (detail) {
title = [detail title];
} else {
title = #"default empty title";
}
Or if you prefer the KVC variant:
id detail = parsedDetails.firstObject;
if (detail) {
title = [detail valueForKey:#"title"];
} else {
title = #"default empty title";
}
Part 2: Updating the label
As far as I understand your comments, you have a NSString property called titleText? Presumably defined like this:
#property (nonatomic, strong) IBOutlet NSString *titleText;
And you also have somewhere a UILabel outlet?
#property (weak, nonatomic) IBOutlet UILabel *label;
If you just update the local string it will not be reflected in the UI. You yet have to transfer it to the label.
This would look like so:
self.label.text = self.titleText;