How to setup a custom UIWindow, UICollectionViewController, UICollectionView, and UICollectionViewCell in a iOS9 swift project

AppDelegate.swift

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?
    var controller = Controller()
    
    override init() {
        super.init()
        self.window = UIWindow(frame: UIScreen.mainScreen().bounds)
    }

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        window!.rootViewController = Controller()
        window!.makeKeyAndVisible()
        return true
    }
}

class Controller: UICollectionViewController {
    var numbers = [1,2,3,4]

    init() {
        super.init(collectionViewLayout: UICollectionViewFlowLayout())
    }
    
    override func loadView() {
        super.loadView()
        self.collectionView = ListView() // delegate and data source are set automatically
    }
    
    override func viewDidLoad() {
        view.backgroundColor = UIColor.whiteColor()
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    
    override func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return numbers.count
    }
    
    override func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
        return 1
    }
    
    override func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCellWithReuseIdentifier(CellIdentifier, forIndexPath: indexPath) as! Cell
        
        configureCell(cell, indexPath: indexPath)
        
        return cell
    }
    
    func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
        return CGSizeMake(collectionView.frame.size.width, 44)
    }
    
    override func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
        let total = numbers[indexPath.row] + numbers.last!
        self.numbers = []
        
        for i in 1...total {
            self.numbers.append(i)
        }
        
        dispatch_async(dispatch_get_main_queue()) {
            self.collectionView!.reloadData()
        }
    }
    
    func configureCell(cell: Cell, indexPath: NSIndexPath) {
        let message = numbers[indexPath.row].description
        cell.text.text = message
    }
}

let CellIdentifier = "converstaionCell"

class ListView: UICollectionView {
    init() {
        super.init(frame: CGRectZero, collectionViewLayout: UICollectionViewFlowLayout())
        registerClass(Cell.self, forCellWithReuseIdentifier: CellIdentifier)
        self.backgroundColor = UIColor.clearColor()
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

class Cell: UICollectionViewCell {
    let text: UILabel
    
    override init(frame: CGRect) {
        self.text = UILabel(frame: CGRect(x: 10, y: 5, width: frame.size.width - 20, height: 24))
        text.font = UIFont.systemFontOfSize(17.0)
        text.textAlignment = .Left
        text.textColor = UIColor.blackColor()
        
        super.init(frame: frame)

        self.backgroundColor = UIColor.clearColor()
        
        contentView.addSubview(text)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}