如何在 static 表視圖上設置協議和委托？

Question

我正在嘗試設置一個 static 表視圖，該表視圖與另一個帶有列表的表視圖有一個segue。 然后用戶從列表中選擇一個項目，並更新主（靜態）表視圖。 我有設置代表，但我認為我遺漏了一些東西。 從列表中選擇一個項目時，它會引發“強制展開可選時意外找到'nil'”的異常。 看來可選的是協議本身。

錯誤截圖

Storyboard示意圖

主表視圖文件

//
//  AddAssetTableViewController.swift
//  ItemizePro
//
//  Created by Tyler Wasick on 5/27/20.
//  Copyright © 2020 Tyler Wasick. All rights reserved.
//

import UIKit

class AddAssetTableViewController: UITableViewController {

    // TODO: Add image IBOutlet

    @IBOutlet weak var nameTextField: UITextField!

    @IBOutlet weak var descriptionTextField: UITextField!

    @IBOutlet weak var datePurchasedTextField: UITextField!

    @IBOutlet weak var manufactureTextField: UITextField!

    @IBOutlet weak var modelTextField: UITextField!

    @IBOutlet weak var serialNumberTextField: UITextField!

    @IBOutlet weak var costTextField: UITextField!

    @IBOutlet weak var roomTextField: UITextField!

    @IBOutlet weak var notesTextView: UITextView!

    @IBOutlet weak var receiptTextField: UITextField!

    @IBOutlet weak var addUIButton: UIButton!

    override func viewDidLoad() {
        super.viewDidLoad()

        // Uncomment the following line to preserve selection between presentations
        // self.clearsSelectionOnViewWillAppear = false

        // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
        // self.navigationItem.rightBarButtonItem = self.editButtonItem


    }

    // MARK: - Table view data source

    /*
     override func numberOfSections(in tableView: UITableView) -> Int {
     // #warning Incomplete implementation, return the number of sections
     return 0
     }

     override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
     // #warning Incomplete implementation, return the number of rows
     return 0
     }


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

     // Configure the cell...

     return cell
     }
     */

    /*
     // Override to support conditional editing of the table view.
     override func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
     // Return false if you do not want the specified item to be editable.
     return true
     }
     */

    /*
     // Override to support editing the table view.
     override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCell.EditingStyle, forRowAt indexPath: IndexPath) {
     if editingStyle == .delete {
     // Delete the row from the data source
     tableView.deleteRows(at: [indexPath], with: .fade)
     } else if editingStyle == .insert {
     // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
     }
     }
     */

    /*
     // Override to support rearranging the table view.
     override func tableView(_ tableView: UITableView, moveRowAt fromIndexPath: IndexPath, to: IndexPath) {

     }
     */

    /*
     // Override to support conditional rearranging of the table view.
     override func tableView(_ tableView: UITableView, canMoveRowAt indexPath: IndexPath) -> Bool {
     // Return false if you do not want the item to be re-orderable.
     return true
     }
     */

    /*
     // MARK: - Navigation

     // In a storyboard-based application, you will often want to do a little preparation before navigation
     override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
     // Get the new view controller using segue.destination.
     // Pass the selected object to the new view controller.
     }
     */

    // MARK: - Functions


    // MARK: - IBAction outlets

    @IBAction func addButtonTapped(_ sender: UIButton) {


    }

}

extension AddAssetTableViewController : RoomDelegate {
    func tappedOnRoom(room: String) {
        roomTextField.text = room
    }
}

帶有項目（房間）列表到 select 的表視圖，它被傳遞回第一個表視圖 controller

//
//  RoomListViewController.swift
//  ItemizePro
//
//  Created by Tyler Wasick on 5/25/20.
//  Copyright © 2020 Tyler Wasick. All rights reserved.
//

import UIKit

protocol RoomDelegate {
    func tappedOnRoom(room: String)
}
class RoomListViewController : UIViewController {

    var selectionDelegate : RoomDelegate!

    @IBOutlet weak var tableView: UITableView!

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.

        // Configure table view
        tableView.dataSource = self
        tableView.delegate = self

    }


    // When user taps on a room, it returns the room to the delagate and dismisses
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

        // Assign the selection to 'selectedRoom'
        let selectedRoom = UserSettings.roomList[indexPath.row]

        // Return the room to the delegate
        selectionDelegate.tappedOnRoom(room: selectedRoom)
    }
}

extension RoomListViewController: UITableViewDataSource, UITableViewDelegate {

    // UITableViewDelegate
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return UserSettings.roomList.count
    }

    // UITableViewDataSource
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        // Setup cell
        let cell = tableView.dequeueReusableCell(withIdentifier: "RoomListCell", for: indexPath) as! RoomListView

        // Set the details for the cell
        let room = UserSettings.roomList[indexPath.row]
        cell.setRoomCell(room)

        // Return the cell
        return cell
    }

}

Answer 1

崩潰是由於您使用了未為其提供值的強制解包委托。

---

使您的Protocol class 綁定：這將允許您創建對您的委托的弱引用

protocol RoomDelegate: class {
    func tappedOnRoom(room: String)
}

使您的委托變得弱且可選：

weak var selectionDelegate: RoomDelegate?

在 AddAssetTableViewController 的prepareForSegue方法中設置委托。 這是您缺少的代碼。

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if let vc = segue.destination as? RoomListViewController {
        vc.selectionDelegate = self
    }
}

調用委托時使用可選鏈

selectionDelegate?.tappedOnRoom(room: selectedRoom)