Example ViewController with CollectionView

GenreViewController.swift

//
//  GenreViewController.swift
//
//  Created by Vasiliy Savchuk on 09.02.17.
//  Copyright © 2017 All rights reserved.
//

class GenreViewController: BaseViewController {
    @IBOutlet weak var mainGenreCollectionView: UICollectionView!
    var viewModel = GenreViewModel()
    
    //MARK: - Lifecicle Object
    
    override func viewDidLoad() {
        super.viewDidLoad()
        load()
        addRefreshControl()
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        self.updateStatusBarUI()
    }
    
    //MARK: - Methods
    
    func updateStatusBarUI() {
        UIApplication.shared.statusBarStyle = UIStatusBarStyle.lightContent
    }
    
    private func load() {
        view.showProgress()
        viewModel.loadViewModels(handler: { [weak self] in
            self?.mainGenreCollectionView.reloadData()
            self?.view.hideProgress()
        })
    }
    
    override func updateUI() {
        guard Reachability.sharedInstance.isReachable else {
            self.mainGenreCollectionView.hidden()
            self.informView.showMe()
            return
        }
        self.informView.hidden()
        self.mainGenreCollectionView.showMe()
    }
    
    func addRefreshControl() {
        self.mainGenreCollectionView.addSubview(self.createRefreshControl())
        self.mainGenreCollectionView.alwaysBounceVertical = true
    }
    
    //MARK: Actions
    
    @IBAction func backButtonDidPress(_ sender: Any) {
        _ = self.navigationController?.popViewController(animated: true)
    }
}

//MARK: - UICollectionViewDataSource

extension GenreViewController: UICollectionViewDataSource {
    
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return viewModel.dataSource.count
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let type = viewModel.moduleType(index: indexPath.row)
        let title = viewModel.moduleName(type: type)
        let subViewModel = viewModel.dataSource[indexPath.row]

        switch type {
            
        case .randomMusicCell:
            let playRandomCell = mainGenreCollectionView.dequeueReusableCell(withReuseIdentifier: PlayRandomCollectionViewCell.className,
                                                                        for: indexPath) as! PlayRandomCollectionViewCell
            playRandomCell.viewModel = subViewModel
            let track: Track = subViewModel.dataSource[indexPath.row] as! Track
            playRandomCell.fillWith(model: track)
            return playRandomCell
            
        case .playlistsCell:
            let playlistsCell = mainGenreCollectionView.dequeueReusableCell(withReuseIdentifier: AlbumsCollectionViewCell.className,
                                                                         for: indexPath) as! AlbumsCollectionViewCell
            
            playlistsCell.titleLabel.text = NSLocalizedString(title, comment: "")
            playlistsCell.viewModel = subViewModel
            playlistsCell.configureGenrePlaylistView(withAllPlaylist: true)
            playlistsCell.collectionView.reloadData()
            return playlistsCell
            
        default:
            let albumsCell = mainGenreCollectionView.dequeueReusableCell(withReuseIdentifier: AlbumsCollectionViewCell.className,
                                                                    for: indexPath) as! AlbumsCollectionViewCell
            
            albumsCell.collectionView.backgroundColor = (indexPath.row % 2) != 0 ? #colorLiteral(red: 1, green: 1, blue: 1, alpha: 1) : #colorLiteral(red: 0.9625374675, green: 0.9625598788, blue: 0.9625478387, alpha: 1)
            albumsCell.titleLabel.text = NSLocalizedString(title, comment: "")
            albumsCell.viewModel = subViewModel
            albumsCell.configureGenreAlbumView(withAllAlbums: true)
            albumsCell.collectionView.reloadData()
            return albumsCell
            
        }
    }
}

//MARK: - UICollectionViewDelegate

extension GenreViewController: UICollectionViewDelegate {
    
    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
        guard Reachability.sharedInstance.isReachable else {
            showInternetAlert()
            return
        }
    }
    
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: IndexPath) -> CGSize {
        let type = viewModel.moduleType(index: indexPath.row)
        
        switch type {
        case .randomMusicCell:
            return PlayRandomCollectionViewCell.size
        case .playlistsCell:
            return AlbumsCollectionViewCell.playlistGanreSize
        default:
            return AlbumsCollectionViewCell.size
        }
    }
}