MVVM for UITableView

mvvm_tableView.swift

import UIKit

struct Album {
    let title: String
}

class SwiftAlbumsTableViewController: UITableViewController {

    @IBOutlet weak private var activityIndicator: UIActivityIndicatorView!

    // THIS IS THE DATA SOURCE
    private var viewAlbums = [Album]()

    // THIS IS THE DATA
    var albums: [Album]? {
        set {
            if let albums = albums {
                // populate data as soon we have it
                viewAlbums = albums
                tableView.reloadData()
            }
        }
        get {
            // empty means no data
            if viewAlbums.isEmpty {
                return nil
            } else {
                return viewAlbums
            }
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        fetchAlbums()
    }

    // MARK: - Table view data source

    override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        // so clean!
        return viewAlbums.count
    }

    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCellWithIdentifier("albumCell", forIndexPath: indexPath) as! UITableViewCell

        // no optionals to think of!
        let album = viewAlbums[indexPath.row]
        cell.textLabel?.text = album.title

        return cell
    }
}

// MARK: API Methods
private extension SwiftAlbumsTableViewController {

    func fetchAlbums() {
        activityIndicator.startAnimating()
        // fetch data assynchronously via your API
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, Int64(2.0 * Double(NSEC_PER_SEC))),
            dispatch_get_main_queue())
            { [weak self] in
                // mimicking data from the API
                self?.albums = [Album(title: "1989"), Album(title: "Fearless"), Album(title: "Red"), Album(title: "Speak Now")]

                // restore UI
                self?.activityIndicator.stopAnimating()
        }
    }
}

interesting idea to split the "data source" into 2 parts.

i have a question here, in what situation, we will reach the code at Line #26?

Wouldn't it ok to just return the empty viewAlbums?