title: Cells are hidden using CollectionView
body: <p>I have a Navigation Controller pushing to a Collection View Controller. This collectionView has an <code>NSArray</code> of images, and I'm sure there are some elements in the collectionView using the method visibleCells.
  But when I launch it there is no displaying cells.
  Here is my code :</p>
  
  <pre><code>- (void)viewDidLoad
  {
      [super viewDidLoad];
  images = [NSArray arrayWithObjects:@"angry_birds_cake.jpg", @"creme_brelee.jpg", @"egg_benedict.jpg", @"full_breakfast.jpg", @"green_tea.jpg", @"ham_and_cheese_panini.jpg", @"ham_and_egg_sandwich.jpg", @"hamburger.jpg", @"instant_noodle_with_egg.jpg", @"japanese_noodle_with_pork.jpg", @"mushroom_risotto.jpg", @"noodle_with_bbq_pork.jpg", @"starbucks_coffee.jpg", @"thai_shrimp_cake.jpg", @"vegetable_curry.jpg", @"white_chocolate_donut.jpg", nil];
  } 
  
  - (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
  return images.count;
  }
  
  - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
  static NSString *identifier = @"Cell";
  
  UICollectionViewCell *cell;
  [collectionView registerClass:[UICollectionViewCell class] forCellWithReuseIdentifier:@"Cell"];
  cell = [collectionView dequeueReusableCellWithReuseIdentifier:identifier forIndexPath:indexPath];
  
  
  NSArray *tab = [collectionView visibleCells];
  for (int i = 0; i &lt; [tab count]; ++i)
  {
      NSLog(@"%d", i);
  }
  [collectionView setBackgroundColor:[UIColor blueColor]];
  
  UIImageView *imageView = (UIImageView *)[cell viewWithTag:100];
  imageView.image = [UIImage imageNamed:[images objectAtIndex:indexPath.row]];
  
  
  return cell;
  }
  </code></pre>
  
  <p>Where am I wrong ? Thanks a lot.</p>