切换视图控制器时变量意外重置为 0

Question

我在名为 DetailViewController 的 ViewController 中有一个名为“results”的变量，它被赋予了一个值，并在 FirstViewController:

中正确打印

extension FirstViewController: UITableViewDataSource{
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return posts.count
    }
     func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "PostCell", for: indexPath) as! PostTableViewCell
        
        cell.typeLabel.text = "Name: \(posts[indexPath.row].typeOfFood)"
        cell.titleLabel.text = "Title: \(posts[indexPath.row].title)"
        cell.locationLabel.text = "Location: \(posts[indexPath.row].location)"
        cell.nameLabel.text = "Name: \(posts[indexPath.row].name)"
        return cell
        
    }
    
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
//        print("Select Row \(indexPath.row)")
        var result = indexPath.row
        tableView.deselectRow(at: indexPath, animated: true)
//        self.performSegue(withIdentifier: "showDetail", sender: nil)
        let mainStoryBoard = UIStoryboard(name: "Main", bundle: Bundle.main)
        guard let detailViewController = mainStoryBoard.instantiateViewController(withIdentifier: "DetailViewController") as? DetailViewController else{
            print("couldnt find vc")
            return
        }
        let detailVC = DetailViewController()
        detailVC.result = indexPath.row
        print(detailVC.result)
        self.present(detailViewController, animated: true, completion: nil)



    }
}

但是当我的应用程序切换到另一个名为 DetailViewController 的 ViewController 时，变量结果始终打印并存储为 0。DetailViewController:

import UIKit
import Firebase
import FirebaseDatabase
class DetailViewController: UIViewController {

    @IBOutlet weak var backButton: UIBarButtonItem!
    @IBOutlet weak var nameOfUserLabel: UILabel!
    @IBOutlet weak var typeOfFoodNeededLabel: UILabel!
    @IBOutlet weak var amountOfFoodNeededLabel: UILabel!
    @IBOutlet weak var reasonNeededLabel: UILabel!
    @IBOutlet weak var descriptionLabel: UILabel!
    @IBOutlet weak var locationLabel: UILabel!
    @IBOutlet weak var imageView: UIImageView!
    @IBOutlet weak var messageButton: UIButton!
     var posts = [Posts]()
    var rowNumber = String()
    var result = Int()
    override func viewDidLoad() {
        super.viewDidLoad()
        var rowNumber = Int()
        loadPosts()
print(result)
//        nameOfUserLabel.text = posts[result].name

    }
    
    func loadPosts() {
        Database.database().reference().child("Posts").observe(.childAdded){(snapshot: DataSnapshot) in
            if let dict = snapshot.value as? [String: Any]{
                
                let titleText = dict["Title"] as! String
                let typeofFoodText = dict["Type of Food"] as! String
                let descriptionText = dict["Description"] as! String
                let amountNeededText = dict["Number of Items Needed"] as! String
                let locationText = dict["Location"] as! String
                let nameText = dict["Name of User"] as! String
                let reasonNeeded = dict["Reason for Donation"] as! String
                
                
                let post = Posts(titleText: titleText, typeOfFoodText: typeofFoodText, descriptionText: descriptionText, amountNeededText: amountNeededText, locationText: locationText, nameText: nameText, reasonNeededText: reasonNeeded)
                 
                self.posts.append(post)
                print(self.posts)

                self.nameOfUserLabel.text = self.posts[self.result].name
                self.descriptionLabel.text = self.posts[self.result].description
                self.typeOfFoodNeededLabel.text = self.posts[self.result].typeOfFood
                self.amountOfFoodNeededLabel.text = self.posts[self.result].amountNeeded
                self.reasonNeededLabel.text = self.posts[self.result].reasonNeeded
                self.locationLabel.text = self.posts[self.result].location

                
                
            }

        }


    }
    ```

我该如何解决这个问题？我主要希望将 FirstViewController 中给出的值传递给 DetailViewController，但它一直重置回 0.

Answer 1

您正在将结果变量传递给新实例 detailVC (detailVC.result)，而传递变量的正确实例是 detailViewController (detailViewController.result).

请在您的共享源代码中替换以下内容：

这个

let mainStoryBoard = UIStoryboard(name: "Main", bundle: Bundle.main)
guard let detailViewController = mainStoryBoard.instantiateViewController(withIdentifier: "DetailViewController") as? DetailViewController else{
                print("couldnt find vc")
                return
            }
let detailVC = DetailViewController()
detailVC.result = indexPath.row
print(detailVC.result)
self.present(detailViewController, animated: true, completion: nil)

与

let mainStoryBoard = UIStoryboard(name: "Main", bundle: nil)
    guard let detailViewController = mainStoryBoard.instantiateViewController(withIdentifier: "DetailViewController") as? DetailViewController else{
                    print("couldnt find vc")
                    return
                }
    detailViewController.result = indexPath.row
    print(detailViewController.result)
    self.present(detailViewController, animated: true, completion: nil)

切换视图控制器时变量意外重置为 0

Variable unexpectedly resetting to 0 when View Controller Switched

variables

xcode

swift

xcode6

swift5