For the SO Question : https://stackoverflow.com/questions/51458807/

ExclusiveCollectionView

//Custom class
class ExclusiveCollectionView : UIView, UICollectionViewDelegate, UICollectionViewDataSource {
    
    @IBOutlet weak var exCollectionView: UICollectionView!
        
    //Inits
 
    class func instanceFromNib() -> ExclusiveCollectionView {
        return UINib(nibName: "ExclusiveCollectionView", bundle: nil).instantiate(withOwner: nil, options: nil)[0] as! ExclusiveCollectionView
    }
     
    override func awakeFromNib() {
        self.prepare()
    }
    
    private func  prepare() {
        self.exCollectionView.delegate = self
        self.exCollectionView.dataSource = self
        self.exCollectionView.register(UINib.init(nibName: "ExclusiveCell", bundle: nil), forCellWithReuseIdentifier: "ExclusiveCell")
        
        let layout = UICollectionViewFlowLayout()
        layout.minimumLineSpacing = 0.0
        layout.minimumInteritemSpacing = 0.0
        layout.itemSize = CGSize.init(width:  self.exCollectionView.frame.size.width/3.0, height:  self.exCollectionView.frame.size.height/2.0) // TODO : Fix the item size distribution problem,
        layout.invalidateLayout()
        self.exCollectionView.collectionViewLayout = layout
    }
    
    
    //MARK:- Collection view delegate
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 6
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "ExclusiveCell", for: indexPath) as! ExclusiveCell
        cell.testLabel.text = "Item : \(indexPath.row)"
        cell.layer.borderWidth = 1.0
        cell.layer.borderColor = UIColor.red.cgColor
        return cell
    }
    
    
}

ViewController

//Parent 
class ViewController: UIViewController {
 
    @IBOutlet weak var myStackView: UIStackView!
 
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let customView = ExclusiveCollectionView.instanceFromNib()
        self.myStackView.addArrangedSubview(customView)
        //    self.customView?.setNeedsLayout()
        //   self.customView?.setNeedsDisplay()
    }
    
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
 
    }
}