radar20948222

import UIKit

class ViewController: UIViewController, UICollectionViewDataSource {
    
    @IBOutlet weak var collectionView: UICollectionView?

    var data = [ "🍅", "🍍", "🍎"  ]

    override func viewDidLoad() {
        super.viewDidLoad()

        func I(item: Int) -> NSIndexPath { return NSIndexPath(forItem: item, inSection: 0) }
        
        // Data contains three items.
        //  0:   🍅
        //  1:   🍍
        //  2:   🍎


        dispatch_async(dispatch_get_main_queue()) {
            // Insert items into data, and reload the others; this is the operation we're describing:
            //  0: M 🍅
            //  1: A 🍆
            //  2: A 🌽
            //  3: A 🍠
            //  4: A 🍇
            //  5: A 🍈
            //  6: A 🍉
            //  7: A 🍊
            //  8: A 🍋
            //  9: A 🍌
            // 10: M 🍍
            // 11: M 🍎

            self.data = [ "🍅", "🍆", "🌽", "🍠", "🍇", "🍈", "🍉", "🍊", "🍋", "🍌", "🍍", "🍎"  ]
            self.collectionView?.performBatchUpdates({ () -> Void in
                self.collectionView?.insertItemsAtIndexPaths([ I(1), I(2), I(3), I(4), I(5), I(6), I(7), I(8), I(9) ])
                self.collectionView?.reloadItemsAtIndexPaths([ I(0), I(10), I(11) ])
                }, completion: nil)
        }
    }

    func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
        return 1
    }
    
    func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return data.count
    }
    
    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCellWithReuseIdentifier("Cell", forIndexPath: indexPath) as! Cell
        cell.label?.text = data[indexPath.item]
        return cell
    }


}

class Cell: UICollectionViewCell {
    
    @IBOutlet weak var label: UILabel?
    
}