title: MBProgressHUD is displayed only when the operation is finished
body: <p>i'm using MBProgressHUD to show a popup with a loading animation but i have a problem. The progress indicator call is executed when i press a button. This is the action </p>
  
  <pre><code>- (IBAction)calendarioButtonPressed:(UIButton *)sender {
  
  MBProgressHUD *hud = [MBProgressHUD showHUDAddedTo:self.view animated:YES];
  hud.mode = MBProgressHUDModeIndeterminate;
  hud.labelText = @"Uploading";
  [hud show:YES];
  [self getCalendarioJson];
  }
  </code></pre>
  
  <p>in the getCalendarioJson i have this</p>
  
  <pre><code>- (void) getCalendarioJson {
  
  //LETTURA CALENDARIO - INIZIO
  NSString *calLink = myLink;
  
  NSData* responseData = [NSData dataWithContentsOfURL:[NSURL URLWithString:calLink]];
  
  
  NSArray* json = [NSJSONSerialization
                   JSONObjectWithData:responseData //1
                   options:kNilOptions error:nil];
  NSDictionary *firstObject = [json objectAtIndex:0];
  
  NSDictionary *cal = [firstObject objectForKey:@"output"];
  variabiliGlobali.calendario = [[NSMutableArray alloc] init];
  for (NSDictionary *dict in cal) {
      [variabiliGlobali.calendario addObject: dict];
  }
  
  //LETTURA CALENDARIO - FINE
  
  }
  </code></pre>
  
  <p>Why does the loading popup appear only at the end of getCalendarioJson execution?
  The button have a segue. When i go back from the target view i can see the popup.</p>
  
  <p>What is the metter? If i delete the segue i can see the popup at the end of getCalendarioJson execution (because there is not a segue).</p>
  
  <p>Thanks in advance.</p>