     }
 
     func shelfView(shelfView: Shelf.View, numberOfItemsInSection section: Int) -> Int {
-        return 20
+        if show1stSection {
+            return 20
+        }
+        return 0
     }
 
     func shelfView(shelfView: Shelf.View, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {


        self.shelfView = shelfView

        let barButtonItem = UIBarButtonItem(title: "reload", style: .Plain, target: self, action: "reload")
        navigationItem.rightBarButtonItem = barButtonItem
    }

    func reload() {
        if let shelfView = shelfView {
            shelfView.beginUpdates()
            shelfView.reloadContentsInSections([0,1], withRowAnimation: .Automatic)
            shelfView.endUpdates()
        }
    }

class ViewController: UIViewController {

    var shelfView: Shelf.View?
    var show1stSection = true

    override func viewDidLoad() {
        super.viewDidLoad()
