ios - swift ，核心数据 : TableView not reloading data when childVC dismissed

Question

好吧，我对此是全新的，并且在阅读许多教程和文章时有点不知所措。并花了几个小时来解决类似的问题，但没有运气解决我自己的问题。我有一个“AddSiteVC”，允许用户添加或删除放入 CoreData 的项目，然后显示在我的“MainVC”上的 TableView 中。我的问题是，当我按保存或删除并返回到我的 MainVC onBtnClick 时，TableView 不会更新，直到我离开 MainVC 然后回来。我不知道我做错了什么，但似乎找不到任何解决这个问题的方法……我不知道我的问题出在哪里，所以我将包括我的大部分 MainVC 代码以供引用。任何帮助将不胜感激!谢谢!

import UIKit
import CoreData

class SitesViewController: UIViewController, UITableViewDelegate, UITableViewDataSource, NSFetchedResultsControllerDelegate {

@IBOutlet weak var tableView: UITableView!

var controller: NSFetchedResultsController<Sites>!

override func viewDidLoad() {
    super.viewDidLoad()

    tableView.delegate = self
    tableView.dataSource = self

    attemptFetch()
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "SitesCell", for: indexPath) as! SitesCell
    configureCell(cell: cell, indexPath: indexPath as NSIndexPath)
    return UITableViewCell()
}

func configureCell(cell: SitesCell, indexPath: NSIndexPath) {
    let sites = controller.object(at: indexPath as IndexPath)
    cell.configureCell(sites: sites)
    cell.accessoryType = .detailButton
}

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "AddSiteViewController" {
        if let destination = segue.destination as? AddSiteViewController {
            if let site = sender as? Sites {
                destination.siteToEdit = site
            }
        }
    }
}

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    if let sections = controller.sections {
        let sectionInfo = sections[section]
        return sectionInfo.numberOfObjects
    }
    return 0
}

func numberOfSections(in tableView: UITableView) -> Int {
    if let sections = controller.sections {
        return sections.count
    }
    return 0
}

func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
    return 75
}

func tableView(_ tableView: UITableView, accessoryButtonTappedForRowWith indexPath: IndexPath) {
    if let objs = controller.fetchedObjects, objs.count > 0 {
        let site = objs[indexPath.row]
        performSegue(withIdentifier: "AddSiteViewController", sender: site)
    }
}

func attemptFetch() {
    let fetchRequest: NSFetchRequest<Sites> = Sites.fetchRequest()
    let alphebaticalSort = NSSortDescriptor(key: "name", ascending: true)
    fetchRequest.sortDescriptors = [alphebaticalSort]

    let controller = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil)
    controller.delegate = self
    self.controller = controller
    do {
        try controller.performFetch()
    } catch {
        let error = error as NSError
        print("\(error)")
    }
}

func controllerWillChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
    tableView.beginUpdates()
}

func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChange anObject: Any, at indexPath: IndexPath?, for type: NSFetchedResultsChangeType, newIndexPath: IndexPath?) {
    switch (type) {
    case.insert:
        if let indexPath = newIndexPath {
            tableView.insertRows(at: [indexPath], with: .fade)
        }
        break
    case.delete:
        if let indexPath = indexPath {
            tableView.deleteRows(at: [indexPath], with: .fade)
        }
        break
    case.update:
        if let indexPath = indexPath {
            let cell = tableView.cellForRow(at: indexPath) as! SitesCell
            configureCell(cell: cell, indexPath: indexPath as NSIndexPath)
        }
        break
    case.move:
        if let indexPath = indexPath {
            tableView.deleteRows(at: [indexPath], with: .fade)
        }
        if let indexPath = newIndexPath {
            tableView.insertRows(at: [indexPath], with: .fade)
        }
        break
    }
}

func controllerDidChangeContent(_ controller: NSFetchedResultsController<NSFetchRequestResult>) {
    tableView.endUpdates()
} 
}

Answer 1

请对代码进行以下更改。因为 viewDidLoad 会在 viewcontroller 加载的时候被调用。但根据您的要求，您在模态页面中添加了一些内容。所以你需要将代码移动到 viewWillAppear

import UIKit
import CoreData

class SitesViewController: UIViewController, UITableViewDelegate, UITableViewDataSource, NSFetchedResultsControllerDelegate {

@IBOutlet weak var tableView: UITableView!

var controller: NSFetchedResultsController<Sites>!

    override func viewDidLoad() {
        super.viewDidLoad()

        tableView.delegate = self
        tableView.dataSource = self


    }

    override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(animated)
        attemptFetch()
    }
}