Nothing happens after calling [table reloadData] when called with dispatch_async - ios

Question

- (void) setRooms:(NSArray *)newRooms
{
NSLog(#"Main thread(cp3)... %d", [rooms count]);
rooms = newRooms;
[table reloadData];
NSLog(#"Main thread(cp4)... %d", [rooms count]);
}
- (void) parseJSONWithURL:(NSURL *)jsonURL
{
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
NSLog(#"Main thread(cp1)...%d", [rooms count]);
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);
dispatch_async(queue, ^{
NSLog(#"Background thread(cp1)...%d", [rooms count]);
NSError *error = nil;
// Request the data and store in a string.
NSString *resp = [NSString stringWithContentsOfURL:jsonURL
encoding:NSASCIIStringEncoding
error:&error];
// Convert the String into an NSData object.
NSData *data = [resp dataUsingEncoding:NSASCIIStringEncoding];
// Parse that data object using NSJSONSerialization without options.
NSDictionary *json = [[NSDictionary alloc] init];
json = [NSJSONSerialization JSONObjectWithData:data
options:kNilOptions
error:&error];
// Return to the main thread to update the UI elements
dispatch_sync(dispatch_get_main_queue(), ^{
NSLog(#"Main thread(cp2)...%d", [rooms count]);
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
[self setRooms:[json valueForKey:#"Rooms"]];
});
NSLog(#"Background thread(cp2)...%d", [rooms count]);
});
NSLog(#"Main thread(cp5)...%d", [rooms count]);
}

Answer 1

Try this
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);
dispatch_async(queue, ^{
NSError *error = nil;
// Request the data and store in a string.
NSString *resp = [NSString stringWithContentsOfURL:jsonURL
encoding:NSASCIIStringEncoding
error:&error];
if (error == nil) {
// Convert the String into an NSData object.
NSData *data = [resp dataUsingEncoding:NSASCIIStringEncoding];
// Parse that data object using NSJSONSerialization without options.
NSDictionary *json = [[NSDictionary alloc] init];
json = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
dispatch_sync(dispatch_get_main_queue(), ^{
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
_rooms = [json valueForKey:#"Rooms"];
[_table reloadData];
});
}
});
or try
[self performSelectorOnMainThread:#selector(udpateAfterFetch:) withObject: [json valueForKey:#"Rooms"] waitUntilDone:YES];
-(void)udpateAfterFetch:(NSArray or whatever *) yourObject
{
_rooms = yourObject;
[_table reloadData];
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
}
The table is not being reloaded because any UI update should happen in the main thread and it is not happening so in ur lines of code.