How to get data from a selected UICollectionView cell?

You can use indexPathsForSelectedItems to get the indexPaths for all selected Items. After you requested all the IndexPath you can simply ask the collectionView for the corresponding cell to get your Data.

import UIKit

class TestCell: UICollectionViewCell {
    var data : String?
}

class ViewController: UIViewController {

    var model = [["1","2","3","4"]]
    @IBOutlet weak var collectionView: UICollectionView?

    @IBAction func buttonTapped(sender: AnyObject) {
        if let collectionView = self.collectionView,
            let indexPath = collectionView.indexPathsForSelectedItems?.first,
            let cell = collectionView.cellForItem(at: indexPath) as? TestCell,
            let data = cell.data {
                    print(data)
        }
    }
}

extension ViewController : UICollectionViewDataSource {
   func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
        return model.count
   }

   func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
            return model[section].count
   }

   func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
            let cell = collectionView.dequeueReusableCellWithReuseIdentifier("test", forIndexPath: indexPath) as! TestCell
            cell.data = self.model[indexPath.section][indexPath.row]
            return cell
      }
   }