ProductCategoriesPageViewController.swift

ProductCategoriesPageViewController.swift

import UIKit

class ProductCategoriesPageViewController: UIPageViewController {
    
    // MARK: Properties
    
    var categoriesViewPageDelegate: ProductCategoriesPageDelegate?
    var pages = [UIViewController]()
    
    // MARK: Lifecycle
    
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    
    // MARK: ProductCategoriesViewController setup methods
    
    func setupPages(with viewControllers: [UIViewController?], andShow firstPage: Int?)  {
        dataSource = self
        delegate = self
        
        for viewController in viewControllers {
            guard let viewController =  viewController else { break }
            pages.append(viewController)
        }
        
        let firstPage = firstPage ?? 0
        setViewControllers([pages[firstPage]], direction: UIPageViewControllerNavigationDirection.forward, animated: false, completion: nil)
    }
    
    func showViewController(for firstPage: Int?)  {
        let firstPage = firstPage ?? 0
        setViewControllers([pages[firstPage]], direction: UIPageViewControllerNavigationDirection.forward, animated: false, completion: nil)
    }
}


extension ProductCategoriesPageViewController: UIPageViewControllerDataSource {
    
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
        var index = viewController.view.tag
        if (index == 0) || (index == NSNotFound) {
            return nil
        }
        index -= 1;
        return pages[index]
    }
    
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
        var index = viewController.view.tag
        if index == NSNotFound {
            return nil;
        }
        index += 1;
        if index == pages.count {
            return nil;
        }
        return pages[index]
    }
}


extension ProductCategoriesPageViewController: UIPageViewControllerDelegate {
    
    func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
        if completed {
            guard let index = pageViewController.viewControllers?.last?.view.tag else { return }
            categoriesViewPageDelegate?.onPageChanged(index)
        }
    }
}