Question

我已经研究过这个问题，我几乎可以肯定我的代码是正确的，但显然有些问题。我有两个控制器。一个有TableView，另一个是带标签的视图控制器。我希望将用户选择的tableview单元格中的单元格文本标签的值发送到第二个视图控制器。很简单。这是我的控制器：

import UIKit
import CoreData

class FavoritesViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {

var selectedFavorite = ""

var specifiedFavorite:String!

let appDelegate = UIApplication.shared.delegate as! AppDelegate

var passages = [NSManagedObject]()

//This code creates the number of cells equal the number of items in the object
public func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {

    return passages.count

}


// The code below displays the passage reference as the cell title
public func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    // This creates the cell for the table. The dequeueReusableCell option ensures the table is scrollable
    let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath) as UITableViewCell

    // this creates a variable for the record defined at the index that is numbered by the indexPath.row.
    let favorite = passages[indexPath.row]
    // We then find the value of the key we want to set for the cell label value
    cell.textLabel!.text = favorite.value(forKey: "reference") as? String

    return cell

}


// This code detects the cell selected and captures a variable that is passed in the segue
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

    let selectedCell = tableView.cellForRow(at: indexPath) as UITableViewCell!

    selectedFavorite = (selectedCell?.textLabel?.text)!

    print("The text in the selected cell is \(selectedFavorite)")

    performSegue(withIdentifier: "toFavoritesDetailsViewController", sender: nil)

    print("Segue performed")

}

//This code is the segue that passes the variable values to the next view
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "toFavoritesDetailsViewController" {

        let favoritesDetailsViewController = segue.destination as! FavoritesDetailsViewController

        favoritesDetailsViewController.specifiedFavorite = selectedFavorite

        print("The variable for selectedFavorite prior to segue is: \(selectedFavorite)")

        print("The variable for favoritesDetailsViewController.specifiedFavorite prior to segue is: \(favoritesDetailsViewController.specifiedFavorite)")

    }
}

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

//This code loads the Core Data Entity into the view
// this is working as evidenced by the tableview being populated with data
    let appDelegate = UIApplication.shared.delegate as! AppDelegate

    let managedContext = appDelegate.persistentContainer.viewContext

    let fetchRequest = NSFetchRequest<NSFetchRequestResult>(entityName:"Passages")
    //
    do {
        let results = try managedContext.fetch(fetchRequest)
        passages = results as! [NSManagedObject]
    } catch let error as NSError {
        print("Could not fetch \(error)")
    }
  }

}

这是我的第二个控制器的代码，名为FavoritesDetailsViewController：

import UIKit
import CoreData

class FavoritesDetailsViewController: UIViewController {

@IBOutlet weak var referenceLabel: UILabel!

@IBOutlet weak var passageText: UITextView!

var specifiedFavorite : String = ""

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    referenceLabel.text? = specifiedFavorite

    print("The viewDidLoad")
    // SMC LEFT OFF HERE
    // Can't get selectedFavorite to load from previous controller
    print("The Value of variable specifiedFavorite sent from segue is: \(specifiedFavorite)")

    print(specifiedFavorite)

    let appDelegate = UIApplication.shared.delegate as! AppDelegate

    let context = appDelegate.persistentContainer.viewContext

    let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Passages")

    request.predicate = NSPredicate(format: "reference = %@", specifiedFavorite)

    request.returnsObjectsAsFaults = false

    do {

        let results = try context.fetch(request)

        print("fetch request was successful")

        if results.count > 0 {

            for result in results as! [NSManagedObject] {

                //                    print("We got results!")

                if let returnedText = result.value(forKey: "passagetext") as? String {

                    print("This is the value of returnedText: \(returnedText)")

                    passageText.text? = returnedText

                    print("This is the text of the selectedFavorite after segue is: \(passageText)")

                }

            }

        }
    } catch {

        print("Couldn't fetch results")

    }


}

override func viewDidLoad() {
    super.viewDidLoad()

    print("The viewDidLoad")

    print("The Value of variable specifiedFavorite sent from segue is: \(specifiedFavorite)")

    print(specifiedFavorite)
}


}

当我运行应用程序时，日志表明变量“specifiedFavorite”的值是在segue之前设置的。

The variable for selectedFavorite prior to segue is: 
The variable for favoritesDetailsViewController.specifiedFavorite prior to segue is: 
The viewDidLoad
The Value of variable specifiedFavorite sent from segue is: 

The text in the selected cell is John 3:16
The variable for selectedFavorite prior to segue is: John 3:16
The variable for favoritesDetailsViewController.specifiedFavorite prior to segue is: John 3:16
2016-12-10 12:43:54.624 Logos to Mind[4036:770173] <UIView: 0x7ff0bf918010; frame = (0 0; 320 568); autoresize = W+H; layer = <CALayer: 0x600000421fa0>>'s window is not equal to <Logos_to_Mind.FavoritesDetailsViewController: 0x7ff0bf9047f0>'s view's window!
Segue performed
The FavoritesDetailsViewController viewDidLoad
The Value of variable specifiedFavorite sent from segue is: 
fetch request was successful

请注意日志消息：从segue发送的变量specifiedFavorite的值是：

是空的。

这是我的问题。我没有看到我的代码中存在哪些错误未能在FavoritesDetailsViewController中设置“specifiedFavorite”变量。我在这里碰到了一堵砖墙。会很感激一些见解。

Answer 1

您的segue是从原型单元连接的。不要为didSelectRowAt而烦恼，因为它是在prepare(for:sender)之后调用的。在prepare(for:sender:)完成所有工作。 sender是触发segue的单元格：

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "toFavoritesDetailsViewController" {

        let favoritesDetailsViewController = segue.destination as! FavoritesDetailsViewController

        if let selectedCell = sender as? UITableViewCell {
            let selectedFavorite = (selectedCell.textLabel?.text)!

            favoritesDetailsViewController.specifiedFavorite = selectedFavorite

            print("The variable for selectedFavorite prior to segue is: \(selectedFavorite)")

            print("The variable for favoritesDetailsViewController.specifiedFavorite prior to segue is: \(favoritesDetailsViewController.specifiedFavorite)")
        }

    }
}

TableView Controller不向变明控制器发送变量

1 个答案: