Swift：如何获取表行单元格（indexPath）并从详细视图控制器的数据模型中加载它？

Question

It took me while to get the core data model working and I can create content in a detail view controller and pass it to my table view to display the newly created row in the table, but I cannot find out how to correctly display the data in the detail view controller again.

Since I am using core data, I was thinking about just getting the index path for the selected table view row and pass it to the detail view controller, where the appropriate data would be loaded from the data model array, but how to pass the indexPath to the detail view controller and load the data?

There is only one barButtonItem in my master view to add new content - plus the tableView.

In my tableView I fetch and display the data like this:

var managedObjectContext: NSManagedObjectContext!    
var coasters = [Coaster]()


override func viewDidLoad() {
        super.viewDidLoad()

        // Add NoteficationCenter observer to reload table from another view.
        NotificationCenter.default.addObserver(self, selector: #selector(loadData), name: NSNotification.Name(rawValue: "reload"), object: nil)

        // Initialize Core Data ManagedObjectContext
        managedObjectContext = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

        loadData()
    }


@objc func loadData() {
        let coasterRequest: NSFetchRequest<Coaster> = Coaster.fetchRequest()

        // Sorting from newest to oldest.
        let sortDescriptors = NSSortDescriptor(key: "date", ascending: false)
        coasterRequest.sortDescriptors = [sortDescriptors]

        // Attempt to load data from Core Data!
        do {
            coasters = try managedObjectContext.fetch(coasterRequest)
            self.tableView.reloadData()
        } catch {
            print("loading error: \(error.localizedDescription)")
        }
    }


override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) as! CoasterTableViewCell

        let coasterItem = coasters[indexPath.row]

        if let coasterImage = UIImage(data: coasterItem.image as! Data) {
            cell.bacgkgroundImageView.image = coasterImage
        }

        cell.nameLabel.text = coasterItem.name
        cell.parkLabel.text = coasterItem.park
        cell.dateLabel.text = coasterItem.date

        cell.countLabel.text = String(coasterItem.counter)

        return cell
    }

To explain this: In the detail view controller everything is saved to core data when the user hits "save" and returns to master view. I added a simple Notification Center observer which is triggered from the detail view controller and tells the master view to reload the data (that was the easiest for me to reload everything without using the prepare function. And it works perfectly.

Now to the problem: So when the user clicks on a table view cell the indexPath should be passed to the detail view and there it should load the correct data from the data model (obviously I guess I have to check whether the user wants to add something or just views the content). How can this be done? I hope this is all you need, if I should add something just ask.

Answer 1

try like this

extension MasterViewController: UITableViewDelegate{
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        //here 'self.tableDataSourceArray' is the data set fetched from the database
        let selectedObject = self.tableDataSourceArray[indexPath.row]
        // pass 'selectedObject' to the detail viewcontroller
        let detail = ......
        detail.currentObjectToDisplay = selectedObject

        //in case, if you are using same view controller to add new info and show the existing info, you are required to take one more property in the detail viewcontroller to handle the data
        detail.addMode = false //'true' if you are adding
    }
}