A simple paged view controller implementation.

PagerViewController.swift

import Foundation
import UIKit

protocol PagerViewControllerDelegate: class {
    func pagerViewController(controller: PagerViewController,
        didUpdatePageCount count: Int)
    func pagerViewController(controller: PagerViewController,
        didUpdatePageIndex index: Int)
}

class PagerViewController: UIPageViewController, UIPageViewControllerDataSource, UIPageViewControllerDelegate {
    
    var pagerDelegate: PagerViewControllerDelegate?
    
    var pages: [UIViewController] = []
    
    var pageControl: UIPageControl = {
        let pageControl = UIPageControl()
        pageControl.translatesAutoresizingMaskIntoConstraints = false
        return pageControl
    }()
    
    convenience init(viewControllers: [UIViewController]) {
        self.init(transitionStyle: .scroll, navigationOrientation: .horizontal, options: nil)
        self.pages = viewControllers
        self.pageControl.numberOfPages = viewControllers.count
    }
    
    override init(transitionStyle style: UIPageViewController.TransitionStyle, navigationOrientation: UIPageViewController.NavigationOrientation, options: [UIPageViewController.OptionsKey : Any]? = nil) {
        super.init(transitionStyle: style, navigationOrientation: navigationOrientation, options: options)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        self.delegate = self
        self.dataSource = self
        
        self.view.addSubview(self.pageControl)
        NSLayoutConstraint.activate([
            self.pageControl.leftAnchor.constraint(equalTo: self.view.leftAnchor),
            self.pageControl.rightAnchor.constraint(equalTo: self.view.rightAnchor),
            self.pageControl.bottomAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.bottomAnchor)
        ])
        
        if let initialViewController = self.pages.first {
            self.scrollToViewController(viewController: initialViewController)
            self.pageControl.currentPage = 0
        }
        self.pagerDelegate?.pagerViewController(controller: self, didUpdatePageCount: self.pages.count)
    }
    
    func scrollToViewController(index newIndex: Int) {
        if let firstViewController = viewControllers?.first,
           let currentIndex = self.pages.firstIndex(of: firstViewController) {
            let direction: UIPageViewController.NavigationDirection = newIndex >= currentIndex ? .forward : .reverse
            let nextViewController = self.pages[newIndex]
            self.scrollToViewController(viewController: nextViewController, direction: direction)
        }
    }
    
    func scrollToViewController(viewController: UIViewController, direction: UIPageViewController.NavigationDirection = .forward) {
        self.setViewControllers([viewController], direction: direction, animated: true, completion: { (finished) -> Void in
            self.pageIndexDidChanged()
        })
    }
    
    func pageIndexDidChanged() {
        if let firstViewController = viewControllers?.first, let index = self.pages.firstIndex(of: firstViewController) {
            self.pageControl.currentPage = index
            self.pagerDelegate?.pagerViewController(controller: self, didUpdatePageIndex: index)
        }
    }
    
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
        guard let viewControllerIndex = self.pages.firstIndex(of: viewController) else {
            return nil
        }
        let previousIndex = viewControllerIndex - 1
        guard previousIndex >= 0 else {
            return self.pages.last
        }
        guard self.pages.count > previousIndex else {
            return nil
        }
        return self.pages[previousIndex]
    }
    
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
        guard let viewControllerIndex = self.pages.firstIndex(of: viewController) else {
            return nil
        }
        let nextIndex = viewControllerIndex + 1
        guard self.pages.count != nextIndex else {
            return self.pages.first
        }
        guard self.pages.count > nextIndex else {
            return nil
        }
        return self.pages[nextIndex]
    }
    
    func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
        self.pageIndexDidChanged()
    }
}