Swift 对象未传入NavigationController
我遇到了一个让我很困惑的问题。我正在将一个项目从Objective-C转换为Swift，并且第一次使用故事板。该应用程序下载RSS数据，并将标题、链接和发布日期存储在CoreData的文章对象中。当用户单击一行时，它将在webView中加载文章 我现在的问题是将Article对象传递给webView。我可以通过放置在tableViewCell上的按钮来传递它，但选择该单元格会导致应用程序崩溃，并且它表示传递给webView的文章对象为零。但是，如果我在用println（）传递它之前测试它，它会显示它不是nil 这是我用于单元格上的按钮的代码Swift 对象未传入NavigationController,swift,uinavigationcontroller,Swift,Uinavigationcontroller,我遇到了一个让我很困惑的问题。我正在将一个项目从Objective-C转换为Swift，并且第一次使用故事板。该应用程序下载RSS数据，并将标题、链接和发布日期存储在CoreData的文章对象中。当用户单击一行时，它将在webView中加载文章 我现在的问题是将Article对象传递给webView。我可以通过放置在tableViewCell上的按钮来传递它，但选择该单元格会导致应用程序崩溃，并且它表示传递给webView的文章对象为零。但是，如果我在用println（）传递它之前测试它，它会显
@IBAction func article(sender: AnyObject)
{
// Pulling the most recent story to display on the HomeViewController
let fetchRequest = NSFetchRequest(entityName: "Article")
let predicate = NSPredicate(format: "feed == 'FLO Cycling' OR feed == 'Triathlete' OR feed == 'Velo News' OR feed == 'Cycling News' OR feed == 'Ironman'")
fetchRequest.predicate = predicate
let sortDescriptor = NSSortDescriptor(key: "pubDate", ascending: true)
fetchRequest.sortDescriptors = [sortDescriptor]
// Set up NSError for the Fetch
var fetchError : NSError?
// When you perform a fetch the returned object is an array of the Atricle Entities.
let fetchedObjects = self.articleContext.executeFetchRequest(fetchRequest, error: &fetchError) as! [Article]
//Grab the latest Article and place the title in the label in the HomeViewController
self.latestArticle = fetchedObjects.last
// Grab the latestArticleViewController so it can be presented modally. Make sure you set up the storyboard identifier.
self.articleView = self.storyboard!.instantiateViewControllerWithIdentifier("ArticleViewController") as? ArticleViewController
self.articleView!.currentArticle = self.latestArticle
self.articleView!.articleContext = self.articleContext
self.presentViewController(self.articleView!, animated: true, completion: nil)
}
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath)
{
let selectedArticle = self.fetchedResultsController!.objectAtIndexPath(indexPath) as? Article
self.articleView = self.storyboard!.instantiateViewControllerWithIdentifier("ArticleViewController") as? ArticleViewController
self.articleView!.currentArticle = selectedArticle
self.articleView!.articleContext = self.articleContext
println("This is coming from didSelectRowAtIndexPath \(self.articleView!.currentArticle!.link)")
self.navigationController!.pushViewController(self.articleView!, animated: true)
tableView.deselectRowAtIndexPath(indexPath, animated: true)
}
@IBAction func article(sender: AnyObject)
{
// Pulling the most recent story to display on the HomeViewController
let fetchRequest = NSFetchRequest(entityName: "Article")
let predicate = NSPredicate(format: "feed == 'FLO Cycling' OR feed == 'Triathlete' OR feed == 'Velo News' OR feed == 'Cycling News' OR feed == 'Ironman'")
fetchRequest.predicate = predicate
let sortDescriptor = NSSortDescriptor(key: "pubDate", ascending: true)
fetchRequest.sortDescriptors = [sortDescriptor]
// Set up NSError for the Fetch
var fetchError : NSError?
// When you perform a fetch the returned object is an array of the Atricle Entities.
let fetchedObjects = self.articleContext.executeFetchRequest(fetchRequest, error: &fetchError) as! [Article]
//Grab the latest Article and place the title in the label in the HomeViewController
self.latestArticle = fetchedObjects.last
// Grab the latestArticleViewController so it can be presented modally. Make sure you set up the storyboard identifier.
self.articleView = self.storyboard!.instantiateViewControllerWithIdentifier("ArticleViewController") as? ArticleViewController
self.articleView!.currentArticle = self.latestArticle
self.articleView!.articleContext = self.articleContext
self.presentViewController(self.articleView!, animated: true, completion: nil)
}
class ArticleViewController: UIViewController, UIWebViewDelegate, MFMailComposeViewControllerDelegate
{
// Properties
var currentArticle : Article?
}
let selectedArticle = self.fetchedResultsController!.objectAtIndexPath(indexPath) as? Article
self.articleView!.currentArticle = selectedArticle
self.latestArticle = fetchedObjects.last
self.articleView!.currentArticle = self.latestArticle
Jon您调用var currentArticle时，它还没有初始化，我在您的pic中看到您已经在代码中进行了一些延迟初始化，请重复此变量，所有操作都应该可以正常开始，我在下面添加了一个示例：
lazy var currentArticle: Article = {
let article = Article()
//any other initialization you need
return article
}()
我希望这对你有帮助 我不明白为什么这样解决了这个问题，但我会解释我做了什么。也许有人有更多的故事板经验可以解释 对于RSS解析器排序的每个提要，我使用了几个ViewController。因为所有文章都以相同的格式显示，所以我使用了一个ArticleViewController来显示文章。下图显示了故事板的整体层次结构。最右边的VC是ArticleViewController，左边的七个是RSS提要的VC 我为每个RSS提要创建了一个segue，以指向ArticleViewController。每个人都有一个唯一的名字，我可以在prepareForSegue中使用。您可以在下面的缩放视图中看到分段 最初，我尝试使用prepareForSegue方法和以下代码将Article对象传递给ArticleViewController
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?)
{
if segue.identifier == "floArticleSegue"
{
if let indexPath = self.storyTableView.indexPathForSelectedRow() {
let object = self.fetchedResultsController.objectAtIndexPath(indexPath) as! Article
(segue.destinationViewController as! ArticleViewController).currentArticle = object
}
}
}
let selectedArticle = self.fetchedResultsController!.objectAtIndexPath(indexPath) as? Article
self.articleView = self.storyboard!.instantiateViewControllerWithIdentifier("ArticleViewController") as? ArticleViewController
self.articleView!.currentArticle = selectedArticle
self.articleView!.articleContext = self.articleContext
println("This is coming from didSelectRowAtIndexPath \(self.articleView!.currentArticle!.link)")
self.navigationController!.pushViewController(self.articleView!, animated: true)
tableView.deselectRowAtIndexPath(indexPath, animated: true)
Jon你能告诉我们你是如何声明和初始化currentArticle的吗？我在末尾添加了代码。如果您还想看其他内容，请告诉我。我尝试了一下，并抛出了两个错误。你可以在上面帖子的末尾看到它们。感谢您提供的信息。您的文章类似乎也依赖于要初始化的其他变量。我建议您创建一个新的变量作为字符串，以保存您正在传递的值，并使用该字符串以旧的方式初始化您的文章。让我知道它是否有效