Page View Controller with Custom Tab Bar

ListViewController.swift

//
//  ListViewController.swift
//  welbe
//
//  Created by Ben Norris on 12/3/15.
//  Copyright © 2015 O.C. Tanner Corporation. All rights reserved.
//

import UIKit

class ListViewController: UITableViewController {
    
    enum ListType: Int {
        case Upcoming
        case Declined
        case Completed
        
        static var count: Int {
            if _count > 0 { return _count }
            while let _ = ListType(rawValue: ++_count) {}
            return _count
        }
        private static var _count = 0
    }
  }
  

RootViewController.swift

//
//  RootViewController.swift
//  welbe
//
//  Created by Ben Norris on 12/8/15.
//  Copyright © 2015 O.C. Tanner Corporation. All rights reserved.
//

import UIKit

class RootViewController: UIViewController, SegueHandlerType {
    
    enum SegueIdentifier: String {
        case EmbedPageViewController = "EmbedPageViewController"
    }
    
    private var pageViewController: UIPageViewController?

    @IBOutlet weak var customTabBar: CustomTabBar!
    
    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
        let board = UIStoryboard(name: "Storyboard", bundle: nil)
        guard let list = board.instantiateViewControllerWithIdentifier(ListViewController.storyboardIdentifier) as? ListViewController else { fatalError("Expected to get ListViewController") }
        guard let pageViewController = pageViewController else { fatalError("Should have page view controller") }
        pageViewController.setViewControllers([list], direction: .Forward, animated: false, completion: nil)
        
        customTabBar.titles = ["Upcoming", "Declined", "Completed"]
        customTabBar.delegate = self
    }
    

    // MARK: - Navigation

    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        switch segueIdentifierForSegue(segue) {
        case .EmbedPageViewController:
            guard let pageViewController = segue.destinationViewController as? UIPageViewController else { fatalError("Expected to get Page View Controller") }
            pageViewController.dataSource = self
            pageViewController.delegate = self
            self.pageViewController = pageViewController
        }
    }

}


// MARK: - Page view controller data source

extension RootViewController: UIPageViewControllerDataSource {
    
    func pageViewController(pageViewController: UIPageViewController, viewControllerBeforeViewController viewController: UIViewController) -> UIViewController? {
        guard let currentList = viewController as? ListViewController else { fatalError("Must have a list for page view controller functionality") }
        if currentList.listType.rawValue > 0 {
            let previousIndex = currentList.listType.rawValue - 1
            return navigationTarget(previousIndex)
        } else {
            return nil
        }
    }
    
    func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController? {
        guard let currentList = viewController as? ListViewController else { fatalError("Must have a list for page view controller functionality") }
        if currentList.listType.rawValue < ListViewController.ListType.count - 1 {
            let endIndex = currentList.listType.rawValue + 1
            return navigationTarget(endIndex)
        } else {
            return nil
        }
    }
    
}


// MARK: - Page view controller delegate

extension RootViewController: UIPageViewControllerDelegate {
    
    func pageViewController(pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
        guard let list = pageViewController.viewControllers?.first as? ListViewController else { fatalError("Expected a list") }
        customTabBar.selectedIndex = list.listType.rawValue
    }
    
}


// MARK: - Custom tab bar delegate

extension RootViewController: CustomTabBarDelegate {
    
    func tabBar(tabBar: CustomTabBar, didSelectTab tab: Int) {
        guard let pageViewController = pageViewController, currentViewController = pageViewController.viewControllers?.first as? ListViewController else { fatalError("Must have pageViewController to scroll") }
        guard let targetViewController = navigationTarget(tab) where targetViewController != currentViewController else { return }
        let forward = currentViewController.listType.rawValue < tab
        pageViewController.setViewControllers([targetViewController], direction: forward ? .Forward : .Reverse, animated: true, completion: nil)
    }
    
}


// MARK: - Private methods

private extension RootViewController {
    
    func navigationTarget(index: Int) -> UIViewController? {
        let board = UIStoryboard(name: "Storyboard", bundle: nil)
        if let newListType = ListViewController.ListType(rawValue: index), newList = board.instantiateViewControllerWithIdentifier(ListViewController.storyboardIdentifier) as? ListViewController {
            newList.listType = newListType
            return newList
        }
        return nil
    }
}