viewController没有被正确删除? [英] viewController not being removed properly?

问题描述

在我的viewController中，我有一个 NSFetchedResultsController 用于填充 tableView .在 viewDidLoad()中，我将当前时间保存到变量中，然后在 NSFetchedResultsController的 didChange AnyObject 回调中将其打印出来:

In my viewController I have an NSFetchedResultsController for populating a tableView. In the viewDidLoad() I'm saving the current time to a variable, then printing it out in the NSFetchedResultsController's didChange AnyObject callback:

class MyViewController: UIViewController, NSFetchedResultsControllerDelegate {
    var date: Date!
    var fetchedResultsController: NSFetchedResultsController<Event>!
   
    override func viewDidLoad() {
        super.viewDidLoad()
        date = Date()
    }

    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
        switch type {
        case .insert:
            feedTable.insertRows(at: [newIndexPath!], with: .fade)
            print(date)
        default:
            break
    }
}

我注意到，当我离开该视图然后返回时，此回调被调用两次，并打印了我第一次进入该视图时的日期以及新的视图:

I noticed that when I leave this view then come back this callback is called twice and the date from the first time I was in the view is printed as well as the new one:

2017-05-14 18:29:42 +0000

2017-05-14 18:29:42 +0000

2017-05-14 18:30:01 +0000

2017-05-14 18:30:01 +0000

我将视图留在这样的单独函数中:

I'm leaving the view in a seperate function like this:

let storyboard = UIStoryboard(name: "Main", bundle: nil)
let controller = storyboard.instantiateViewController(withIdentifier: "HomePage") as? HomeVC
controller?.managedObjectContext = self.managedObjectContext
self.present(controller!, animated: true, completion: nil)

为什么即使我离开并回来后，这个 MyViewController 似乎仍然存在?我离开它的方式是否无法正确删除?

Why does this MyViewController seem to stick around even after I leave it and come back? Is the way I'm leaving it not removing it properly?

推荐答案

我将视图留在这样的单独函数中:

I'm leaving the view in a seperate function like this:

let storyboard = UIStoryboard(name: "Main", bundle: nil)
let controller = storyboard.instantiateViewController(withIdentifier: "HomePage") as? HomeVC
controller?.managedObjectContext = self.managedObjectContext
self.present(controller!, animated: true, completion: nil)

是的，就是这个问题.而不是返回到现有的HomeVC，而是创建一个新 HomeVC，并在您自己的上方显示 .因此，您只需不断堆积视图控制器即可.

Yup, that's the problem. Instead of returning to the existing HomeVC, you're making a new HomeVC and presenting that on top of yourself. So you just keep piling up the view controllers.

您需要做的就是回到家，放松一下在这里所做的事情.如果存在，则现在关闭.如果是 push ，现在是 pop .

What you need to do to get back home is unwind what you did to get here. If present, now dismiss. If push, now pop.

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