How to use custom fonts that respond to Dynamic Type size changes.

DynamicTypeWithCustomFonts

NSNoticationCenter *center = [NSNotificationCenter defaultCenter];
[center addObserver: self selector:@selector(dynamicTypeChanged:) name: UIContentSizeCategoryDidChangeNotification
          object:nil];

- (void) dynamicTypeChanged:(NSNotification *) note {

  UIApplication *app = [UIApplication sharedApplication];
  NSString *category = app.preferredContentSizeCategory;
  
  if ([category isEqual:UIContentSizeCategorySmall]) {
    ...
  } else if ([category isEqual:UIContentSizeCategoryMedium]) {
    ...
  } else if ([category isEqual:UIContentSizeCategoryLarge]) {
    ...
  } else ...



}