title: In UIViewController's code, [self.subViewGrid setNeedsDisplay] not calling -drawRect
body: <p>I have an <code>iPad</code> app, using <code>Storyboards</code>, <code>XCode 4.6</code> and <code>iOS 6.1</code>.  I have a scene that contains a <code>UIViewController</code>.  Inside that <code>UIViewController</code>, I have a <code>UIScrollController</code>, all created using IB.  Programmatically, in <code>viewDidLoad</code> I created two (2) <code>UIViews</code> (one called <code>subViewGrid</code>, the other called <code>subViewData</code>) and added them to the <code>UIViewController</code>; they both display correctly in the Simulator.  Here's the code:</p>
  
  <pre><code>- (void)viewDidLoad  {
  
  [super viewDidLoad];
  
  // notify me when calendar has been tapped and CFGregorianDate has been updated
  [[NSNotificationCenter defaultCenter] removeObserver:self];
  [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(calendarTapNotification:)
                                               name:@"calendarDateSelected" object:nil ];
  
  //   UIScrollVIew settings
  CGSize scrollableSize = CGSizeMake(760, 1379);  //  set size of scheduleView
  [self.schedScrollView setContentSize:scrollableSize];
  self.schedScrollView.contentInset = UIEdgeInsetsMake(0,0,44,44);  //  allow for scroll bar
  self.schedScrollView.directionalLockEnabled = YES;  //  prevents diagonal scrolling
  
  //  create a sub-view to hold the appointment GRID
  CGRect frame = CGRectMake(0,0,760,1390);  //  110,48,760,1390
  subViewGrid = [[UIView alloc] initWithFrame:frame];
  subViewGrid.tag = 12;  //  use tag to get correct sub-view
  subViewGrid.backgroundColor = [UIColor grayColor];
  subViewGrid.alpha = 1.0;  //  make it opaque
  [self.schedScrollView addSubview:subViewGrid];
  
  //  create a sub-view to hold the appointment DATA
  frame = CGRectMake(110,48,670,750); 
  subViewData = [[UIView alloc] initWithFrame:frame];
  subViewData.tag = 22;  //  use tag to get correct sub-view
  subViewData.backgroundColor = [UIColor redColor];
  subViewData.alpha = 0.2;  //  make it sort of transparent
  [self.schedScrollView addSubview:subViewData];
  
  [self.subViewGrid setNeedsDisplay];  //  ****  UPDATED ****
  </code></pre>
  
  <p>}</p>
  
  <p>Here is the <code>.h</code> file contents for the <code>UIViewController</code>:</p>
  
  <pre><code>    @interface CalendarViewController : UIViewController  {
  
      UIView *subViewGrid;
      UIView *subViewData;
  
  }
  
  @property (strong, nonatomic) IBOutlet UIScrollView *schedScrollView;
  
  - (void) calendarTapNotification:(NSNotification *) notification;
  -(NSDate *)beginningOfDay:(NSDate *)date;
  -(NSDate *)endOfDay:(NSDate *)date;
  
  @end
  </code></pre>
  
  <p>In my <code>drawRect</code> method, I have some code that is supposed to draw a "grid" on the subViewGrid.  The problem is <code>drawRect</code> never gets called.`</p>
  
  <p>I have read the <code>UIView</code> Programmer's Guide and looked in SO and did a Google search, but found nothing that addresses the issue, which is: why won't <code>[self.subViewGrid setNeedsDisplay]</code> call <code>drawRect</code> from where I have it placed?</p>