Demo.swift

class MainViewController: UIViewController() {
    var viewModel = WebsiteList()
    
    func tabsButtonPressed() {
        let vc = ListView(vm: viewModel)
        // present the vc
    }
}

class ListView: UIViewController {
    var viewModel: WebsiteList
    @IBOutlet collectionView: UICollectionView!
    
    convenience init(vm: WebsiteList) {
        viewModel = vm
    }
    
    override func viewDidLoad() {
        collectionView.dataSource = self
    }
    
    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCellWithReuseIdentifier("myCell", forIndexPath: indexPath) as! MyCell
        cell.image = viewModel.imageForIndexPath(indexPath)
        return cell
    }
}

struct WebsiteList {
    var images: [UIImage] = [UIImage]()

    func addImage(image: UIImage) {
        images.append(image)
    }
    
    func imageForIndexPath(indexPath: NSIndexPath) -> UIImage {
        return images[indexPath.row]
    }
}