import UIKit
class MyCollectionViewCell: UICollectionViewCell {
    
    @IBOutlet weak var myLabel: UILabel!
}

@IBOutlet weak var collectionView: UICollectionView!

override func viewDidLoad() {
        super.viewDidLoad()
        collectionView.delegate = self
        collectionView.dataSource = self
    }

let reuseIdentifier = "cell" // also enter this string as the cell identifier in the storyboard
var items = ["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24", "25", "26", "27", "28", "29", "30", "31", "32", "33", "34", "35", "36", "37", "38", "39", "40", "41", "42", "43", "44", "45", "46", "47", "48"]
    

class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate

// tell the collection view how many cells to make
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return self.items.count
    }
    
    // make a cell for each cell index path
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        
        // get a reference to our storyboard cell
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath as IndexPath) as! MyCollectionViewCell
        
        // Use the outlet in our custom class to get a reference to the UILabel in the cell
        cell.myLabel.text = self.items[indexPath.row] // The row value is the same as the index of the desired text within the array.
        cell.backgroundColor = UIColor.cyan // make cell more visible in our example project
        
        return cell
    }
    
    // MARK: - UICollectionViewDelegate protocol
    
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        // handle tap events
        print("You selected cell #\(indexPath.item)!")
    }

class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout {...

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
           let padding: CGFloat =  50
           let collectionViewSize = collectionView.frame.size.width - padding

           return CGSize(width: collectionViewSize/columnsItems, height: collectionViewSize/columnsItems)
       }