在 API 请求后更新 UIPageViewController 的正确方法

Posted 2023-02-24

【中文标题】在 API 请求后更新 UIPageViewController 的正确方法

【英文标题】：Correct way to update UIPageViewController after an API request

【发布时间】：2016-09-16 23:49:51

【问题描述】：

当我尝试使用 Alamofire 执行 GET 请求时遇到问题。在我的 viewDidLoad 方法中。我已经检查了我的请求是否有效并且我的数组已填充，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，数组此时为空。 如果我想使用来自我的 API 的数据创建我的 UIPageViewController，我该怎么做。 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

    

有什么想法？？？

【参考方案1】：

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

需要在不在该范围之外的 alamofire 回调中调用。您从中填充的数组 (arrPageTitle) 在您调用 setViewControllerAtIndex 时将为空，并且您正在使用索引访问数组中的值，从而为您提供越界错误。

你应该在这个 if 作用域的末尾调用函数

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 循环内，具体取决于您想要做什么。

【讨论】：

哦，完美，现在工作正常。非常感谢@Moriya