为什么我的指数不能高于 1？

Question

我正在尝试使用PageViewController生成新的ViewControllers，其数据基于UserDefaults中保存的名称数组。当用户在数组中添加新名称时，PageView应在每次滑动时生成一个新页面，直到索引>=大于array.count。

问题是，当数组中有5个项目时，我可以无限滑动，前两页的索引正常工作，但每次滑动时都保持在1，所以它永远不会变成==或>=，因此它将返回Nil。数组似乎是正确的，当打印它打印5个名称时，但由于某种原因，它在页面中没有正确索引查看，有人能确定问题可能是什么吗？

我希望这是足够的信息，Manager是我持有名为coins的数组的类，该数组目前包含5个加密货币名称，其想法是能够添加一个新页面，附加该数组，这样pageView将生成一个新的页面，从API检索数据，以加载该硬币的特定数据，非常类似于IOS天气应用程序的工作方式。感谢您的帮助，这里是页面的代码ViewController:

import UIKit
class PageViewController: UIPageViewController,
UIPageViewControllerDataSource, UIPageViewControllerDelegate {
//page Control dots
var pageControl = UIPageControl()
func configurePageControl() {
// The total number of pages that are available is based on how
many available colors we have.
pageControl = UIPageControl(frame: CGRect(x: 0,y: UIScreen.main.bounds.maxY - 50,width: UIScreen.main.bounds.width,height: 50))
self.pageControl.numberOfPages = (Manager.shared.coins.count)
self.pageControl.currentPage = 0
self.pageControl.tintColor = UIColor.black
self.pageControl.pageIndicatorTintColor = UIColor.gray
self.pageControl.currentPageIndicatorTintColor = UIColor.white
self.view.addSubview(pageControl)
}
// MARK: Delegate functions
func pageViewController(_ pageViewController: UIPageViewController, didFinishAnimating finished: Bool, previousViewControllers: [UIViewController], transitionCompleted completed: Bool) {
let pageContentViewController = pageViewController.viewControllers![0]
self.pageControl.currentPage = (viewControllers?.index(of: pageContentViewController)!)!
}
func viewControllerAtIndex(_ index: Int, storyboard: UIStoryboard) -> TemplateViewController? {
if Manager.shared.coins.count == 0 || index >= Manager.shared.coins.count {
return nil
}
let templateViewController = storyboard.instantiateViewController(withIdentifier: "templateController") as! TemplateViewController
templateViewController.dataObject = Manager.shared.coins[index]
print(Manager.shared.coins)
return templateViewController
}
func indexOfViewController(_ viewController: TemplateViewController) -> Int {
print(viewController.dataObject)
return Manager.shared.coins.index(of: viewController.dataObject) ?? NSNotFound
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
var index = self.indexOfViewController(viewController as! TemplateViewController)
if (index == 0) || (index == NSNotFound){
return nil
}
index -= 1
return self.viewControllerAtIndex(index, storyboard: viewController.storyboard!)
}
func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
var index = self.indexOfViewController(viewController as! TemplateViewController)
if index == NSNotFound {
return nil
}
index += 1
if index == Manager.shared.coins.count {
return nil
}
return self.viewControllerAtIndex(index, storyboard: viewController.storyboard!)
}
//List of View Controllers.
override func viewDidLoad() {
super.viewDidLoad()
self.delegate = self
configurePageControl()
self.dataSource = self
if let firstViewController = viewControllerAtIndex(0, storyboard: self.storyboard!){
self.setViewControllers([firstViewController], direction: .forward, animated: true, completion: nil)
}
}
}

硬币：

class Manager {
var coins = [""]
let defaults = UserDefaults.standard
static let shared = Manager()
init() {
self.coins = self.defaults.stringArray(forKey: "SavedStringArray") ?? [String]()
}
func addCoin(coin:String) {
self.coins.append(coin)
self.defaults.set(self.coins, forKey: "SavedStringArray")
print ("coins from addCoin:")
print (self.coins)
}
}

我从其他地方添加硬币到阵列中，就像这样：

@IBAction func goButton(_ sender: Any) {
self.choosePerm()
Manager.shared.coins.append(chosenCoin)
Manager.shared.addCoin(coin: chosenCoin)
print(Manager.shared.coins)
print(chosenCoin)
}

编辑：上面我已经编辑了我附加数组的方式，choosePerm((在搜索完成后获得硬币的名称，choosenCoin是搜索后选择的硬币，它肯定是1个名称，但我仍然让它每次都加两个，你能看到可能导致这种情况的原因吗？即打印

["Ethereum", "Boolberry", "Boolberry", "Bitcoin", "Bitcoin"]

Answer 1

您将硬币追加两次：

Manager.shared.coins.append(chosenCoin) // <-- appending for the first time
Manager.shared.addCoin(coin: chosenCoin) // <-- appending for the second time
func addCoin(coin:String) {
self.coins.append(coin) // <-- this is the second appending

这种错误可以修复，但不允许从Manager类外部附加：

private(set) var coins = [""]