ios - 将核心数据值传递到文本字段中以进行编辑/保存

Question

我是使用 Xcode 和 swift 的新手，仍在学习中。我在将核心数据从实体传递到文本字段/标签时遇到问题，然后用户可以选择编辑和保存记录。我的目标是，当用户从 friendslistViewController.swift 单击 tableView 中的单元格时，它会将他们带到 editViewController.swift 屏幕以编辑和保存记录。我想我需要实现 prepareforsegue 函数，但不确定如何实现？

friendsViewController.swift(初始数据输入)

//
//  friendsViewController.swift
// 
//
//  Created by on 11/10/17.
//  Copyright © 2017. All rights reserved.
//

import UIKit
import CoreData

class friendsViewController: UIViewController {

        //OUTLETS


    @IBOutlet weak var firstName: UITextField!        
    @IBOutlet weak var lastName: UITextField!        
    @IBOutlet weak var genderSegControl: UISegmentedControl!        
    @IBOutlet weak var ageStepper: UIStepper!

    //AGECOUNT
    @IBOutlet weak var ageLabel: UILabel!        
    @IBOutlet weak var address: UITextField!

    var context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

    override func viewDidLoad() {
        super.viewDidLoad()    
        // Do any additional setup after loading the view.
    }

    //actions

    @IBAction func ageStepperStep(_ sender: UIStepper) {
        let step = Int(sender.value) // using an integer variable
        ageLabel.text = String(step)
        // label1.text = Int(sender.value).description
        // another way without using any integer variable
    }


    // TEST GENDER
    /*

        var gender : String
        if self.genderSegControl.selectedSegmentIndex == 0 {
            gender = "male"
        }
        else {
            gender = "female"
        }
        genderLabel.text! = gender

 */

   //SAVE FRIEND BUTTON
    @IBAction func saveFriendBtn(_ sender: Any) {

        if firstName.text != "" && lastName.text != "" {               

            var gender : String?
            if self.genderSegControl.selectedSegmentIndex == 0 {
                gender = "male"
            }
            else {
                gender = "female"
            }


            let newFriend = NSEntityDescription.insertNewObject(forEntityName: "Friends", into: context)
            newFriend.setValue(self.firstName.text, forKey: "firstName")
            newFriend.setValue(self.lastName.text, forKey: "lastName")
            newFriend.setValue(self.address.text, forKey: "address")
            newFriend.setValue(self.ageLabel.text, forKey: "age")
            newFriend.setValue(gender, forKey: "gender")

            /*let gender: String = genderSegControl.titleForSegment(at: genderSegControl.selectedSegmentIndex)!
 */


            //SAVE THE CONTEXT
            do {
                try context.save()
            }
            catch{
                print(error)
            }
         }
        else {
            print("please enter your first and last name!")
        }
    }

} //end class

friendslistViewController.swift(显示带有单元格的 tableView 的屏幕)

//
//  friendslistViewController.swift
// 
//
//  Created by on 11/10/17.
//  Copyright © 2017. All rights reserved.
//

import UIKit
import CoreData

class friendslistViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {

    /*
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        var DestViewController : editViewController = segue.destinationViewController as! editViewController

        DestViewController.firstNameInput = name.firstName!
    }
 */

    //outlets

    @IBOutlet weak var tableView: UITableView!

    var userArray:[Friends] = []

    override func viewDidLoad() {
        super.viewDidLoad()            

        tableView.delegate = self
        tableView.dataSource = self

        self.fetchData()
        self.tableView.reloadData()


        // Do any additional setup after loading the view.
    }

    func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }


    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return userArray.count
    }


    //DISPLAY LISTVIEW
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)
        //save first users data into array
        let name = userArray[indexPath.row]
        cell.textLabel!.text = name.firstName! + " " +
            name.lastName! + ", " +
            name.age! + ", " +
            name.gender! + ", " +
            name.address!

        return cell
    }


    func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {

        let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

        if editingStyle == .delete{

            //delete a friend
            let friend = userArray[indexPath.row]
            context.delete(friend)
            (UIApplication.shared.delegate as! AppDelegate).saveContext()

            do{
                userArray = try context.fetch(Friends.fetchRequest())

            }catch{
                print(error)
            }

        }
        tableView.reloadData()

    }

    //fetch the data
    func fetchData(){
        let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

        do{
            userArray = try context.fetch(Friends.fetchRequest())
        }
            //if error exists/catch it
        catch{
            print(error)
        }
    }

    //actions
 } //end class

editViewController.swift(处理编辑/保存的屏幕)

//
//  editViewController.swift
// 
//
//  Created by  on 15/10/17.
//  Copyright © 2017. All rights reserved.
//

import UIKit

import CoreData

class editViewController: UIViewController {

    @IBOutlet weak var firstName: UITextField!        
    @IBOutlet weak var lastName: UITextField!        
    @IBOutlet weak var ageLabel: UILabel!        
    @IBOutlet weak var address: UITextField!

    var firstNameInput = String()

    override func viewDidLoad() {
        super.viewDidLoad()

        firstName.text = firstNameInput

        // Do any additional setup after loading the view.
    }

 }

Answer 1

首先，您应该更改 View Controller 的名称，使它们全部以大写字母开头(例如 class FriendsViewController: UIViewController)，并对文件名执行相同的操作。

其次，您关于需要添加转场的说法是正确的。您查看过 Apple 文档中的 func prepare(for segue: UIStoryboardSegue, sender: Any?) 吗？

您在目标 View Controller (editViewController.swift) 中需要一个变量，您可以将 Friend 对象分配给该变量。在您的 prepare(for:sender:) 方法中，您需要类似 let destinationViewController = segue.destination as!编辑 View Controller 。然后，您可以使用该 destinationViewController 变量来访问目标 View Controller 中的变量并将对象分配给它。

看看你能走多远。