在API请求之后更正UIPageViewController的正确方法

Question

当我尝试使用Alamofire执行GET请求时遇到问题。在我的viewDidLoad方法中。我已经检查过我的请求是否有效以及我的数组是否已填充但是当我运行代码时出现致命错误：索引超出范围，因为当我调用 getViewControllerAtIndex 方法时，数组在此时为空。 如果我想用来自我的API的数据创建我的UIPageViewController，该怎么办？ 这是我在ViewController.swift中的代码

    import UIKit
import Foundation
import Alamofire


class ViewController: UIPageViewController, UIPageViewControllerDataSource {

    var arrPageTitle = [String]()
    var arrPagePhoto = [String]()

    override func viewDidLoad() {
        super.viewDidLoad()

        let guidesEndpoint: String = "http://testapi.eu-gb.mybluemix.net/guides"

        Alamofire.request(guidesEndpoint).responseJSON { (response) in

            if let JSON = response.result.value {

                //print("JSON: \(JSON)")

                if let guides = JSON as? [String : AnyObject] {

                    if let guideResourceList = guides["_embedded"] as? [String : AnyObject] {

                        //print(guideResourceList)
                        if let guidesArray = guideResourceList["guideResourceList"] as? [AnyObject] {

                            for guide in guidesArray {

                                if let guideGuide = guide["guide"] as? [String : AnyObject] {
                                    if let textItem = guideGuide["text"] as? String {
                                        // Populate arrPageTitle
                                        self.arrPageTitle.append(textItem)
                                        print(textItem)
                                    }

                                }

                                if let guideLinks = guide["_links"] as? [String : AnyObject] {
                                    if let linksObj = guideLinks["imageUrl"] as? [String : String] {
                                        if let link = linksObj["href"] {
                                            // Populate arrPagePhoto
                                            self.arrPagePhoto.append(link)
                                            print(link)
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }

        self.dataSource = self
        self.setViewControllers([getViewControllerAtIndex(0)] as [UIViewController], direction: UIPageViewControllerNavigationDirection.forward, animated: false, completion: nil)
    }

    // Use this method to return to previous view. In this I have put a condition such that if it is first view then return nil otherwise return ViewController.
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {

        let pageContent: PageContentViewController = viewController as! PageContentViewController
        var index = pageContent.pageIndex
        if index == 0 || index == NSNotFound {
            return nil
        }
        index -= 1

        return getViewControllerAtIndex(index)
    }

    // MARK:- UIPageViewControllerDataSource Methods

    // Use this method to return next view. In this I have put a condition such that if it is last view then return nil otherwise return ViewController.
    func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {

        let pageContent: PageContentViewController = viewController as! PageContentViewController
        var index = pageContent.pageIndex
        if index == NSNotFound { return nil }
        index += 1
        if index == arrPageTitle.count { return nil }

        return getViewControllerAtIndex(index)
    }



    // MARK:- Custom Methods

    func getViewControllerAtIndex(_ index: Int) -> PageContentViewController {

        // Create a new view controller and pass suitable data.
        let pageContentViewController = self.storyboard?.instantiateViewController(withIdentifier: "PageContentViewController") as! PageContentViewController

        // fatal error: Index out of range
        pageContentViewController.strTitle = "\(arrPageTitle[index])"
        pageContentViewController.strPhotoName = "\(arrPagePhoto[index])"
        pageContentViewController.pageIndex = index
        pageContentViewController.numberOfPages = arrPagePhoto.count
        print("\(arrPagePhoto.count)")

        return pageContentViewController

    }

}

这是我的PageContentViewController.swift

import UIKit

class PageContentViewController: UIViewController {

    @IBOutlet weak var lblTitle: UILabel!
    @IBOutlet weak var imageView: UIImageView!   
    @IBOutlet weak var pageControl: UIPageControl!

    var pageIndex: Int = 0
    var strTitle: String!
    var strPhotoName: String!
    var numberOfPages: Int!

    override func viewDidLoad() {
        super.viewDidLoad()

        imageView.image = UIImage(named: strPhotoName)
        lblTitle.text = strTitle
        pageControl.currentPage = pageIndex
        pageControl.numberOfPages = numberOfPages

    }

}

任何想法???

Answer 1

self.setViewControllers([getViewControllerAtIndex(0)] as [UIViewController], direction: UIPageViewControllerNavigationDirection.forward, animated: false, completion: nil)

需要在alamofire回调中调用，而不是在该范围之外。从（arrPageTitle）填充的数组在调用setViewControllerAtIndex时将为空，并且您正在使用索引访问数组中的值，从而为您提供超出范围的错误。

您应该在此if-scope

的末尾调用该函数

if let guidesArray = guideResourceList["guideResourceList"] as? [AnyObject] {
     //parsing code...
    self.setViewControllers([getViewControllerAtIndex(0)] as [UIViewController], direction: UIPageViewControllerNavigationDirection.forward, animated: false, completion: nil)

}

或在for循环中，取决于你想要做什么。