如何在本地保存数组数据

Question

这是我的代码。我想学习如何为每个单元格的 like 按钮保存我的数据源。这样当用户离开应用并稍后返回时，被点赞的相同单元格仍然被点赞。

这是我上一篇文章的新代码。由于我不想继续制作新数组，我可以尝试在本地保存我的 dataSource 变量，该变量存储每个单元格的被喜欢与否的状态。

ViewController -

import UIKit

class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {


    @IBOutlet var tableView: UITableView!
    
    var dataSource: [TableModel] = []
    var updatedCell = TableViewCell()
    
    var updatedIndex = Int()
    override func viewDidLoad() {
        super.viewDidLoad()
        overrideUserInterfaceStyle = .light
        
            self.dataSource = Array(repeating: TableModel(isLiked: false), count: 8)
            self.tableView.delegate = self
            self.tableView.dataSource = self
            self.tableView.showsVerticalScrollIndicator = false
            self.tableView.reloadData()
    }
    
    @IBAction func buttonSelected(_ sender: Any) {
        // Update Cell for which UIButton (Like Button) was tapped.
        dataSource[(sender as AnyObject).tag].isLiked = !dataSource[(sender as AnyObject).tag].isLiked
        let indexPath = IndexPath(row: (sender as AnyObject).tag, section: 0)
        tableView.reloadRows(at: [indexPath], with: .automatic)
    }
    
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        tableView.deselectRow(at: indexPath, animated: true)
        
        // Saved updatedCell & updatedIndex variables for delegate pattern. To Update this VC's cells data when edited on secondVC (moreInfoViewController) in a way, made them accessible outside this function
        // To Get Specific TableView Cell the user is interacting with.
        updatedCell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! TableViewCell
        updatedIndex = indexPath.row
        
        // Go to Second VC and Send cell tapped data to next view
        let vc = (storyboard?.instantiateViewController(identifier: "secondVC") as? moreInfoViewController)!
        vc.delegate = self
        
        // Get Status of Liked Button in the cell the user tapped and display if the user liked it previously in the SecondVC
        let isLiked = dataSource[indexPath.row].isLiked
        if isLiked {
//            print("Liked")
            vc.isLiked = true
        } else {
//            print("Not Liked")
            vc.isLiked = false
        }
        present(vc, animated: true)
    }
    
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 8
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! TableViewCell
        //        cell.moreBtn.isUserInteractionEnabled = false
        
        cell.likeBtn.tag = indexPath.row
//        cell.likeBtn.addTarget(self, action: #selector(buttonSelected(_:)), for: .touchUpInside)
        
        // Get Each Cell Liked Button Status and display if the user liked or not Liked each cell
        let isLiked = dataSource[indexPath.row].isLiked
        if isLiked {
            // User liked the post
            cell.likeBtn.setImage(UIImage(named: "liked"), for: UIControl.State.normal)
        } else {
            // User Unliked the post
            cell.likeBtn.setImage(UIImage(named: "unLiked"), for: UIControl.State.normal)
        }
        
        return cell
    }
}

// Conform VC to protocol (VC2Delegate) located in "Structs.swift" File
extension ViewController: VC2Delegate {
    func likeStatusDidChange(_ vc2: moreInfoViewController, to title: Bool) {
        // set the text of the table cell here...
        dataSource[updatedIndex].isLiked = !dataSource[updatedIndex].isLiked
        let indexPath = IndexPath(row: updatedIndex, section: 0)
        tableView.reloadRows(at: [indexPath], with: .automatic)
    }
}

moreInfoViewController -

import UIKit

class moreInfoViewController: UIViewController {

    @IBOutlet var backBtn: UIButton!
    @IBOutlet var titleLabel: UILabel!
    @IBOutlet var locationLabel: UILabel!
    @IBOutlet var theImage: UIImageView!
    @IBOutlet var mainlikeBtn: UIButton!
    @IBOutlet var mainTypeLbl: UILabel!
    
    var currentID:String = ""
    var isLiked = Bool()
    weak var delegate: VC2Delegate?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        overrideUserInterfaceStyle = .light
        self.navigationController?.setNavigationBarHidden(true, animated: true)
        styles()
        
        // "isLiked" variable to display whether or user liked this event
        if (isLiked == true) {
            // is Liked
            mainlikeBtn.setImage(UIImage(named: "liked"), for: UIControl.State.normal)
        } else {
            // Not Liked
            mainlikeBtn.setImage(UIImage(named: "unLiked"), for: UIControl.State.normal)
        }
    }
    
    // Heart/Like Button Action. User can like event in this VC with this button and it will tell the firstVC (ViewController) to update "Like Status" there also
    @IBAction func likeBtnAction(_ sender: Any) {
        if (isLiked == true) {
            // is Liked
            isLiked = false
            mainlikeBtn.setImage(UIImage(named: "unLiked"), for: UIControl.State.normal)
        } else {
            isLiked = true
            mainlikeBtn.setImage(UIImage(named: "liked"), for: UIControl.State.normal)
        }
        // When User interacts with like Button, this function gets called that tells the firstVC (ViewController) to update as well.
        // likeStatusDidChange function is located at the bottom of the (ViewController) with extension ViewController.
        delegate?.likeStatusDidChange(self, to: true)
    }
    
    // Go Back To FirstVC (ViewController)
    @IBAction func previousVC(_ sender: Any) {
        dismiss(animated: true, completion: nil)
    }
    
    func styles() {
        titleLabel.numberOfLines = 1
        titleLabel.adjustsFontSizeToFitWidth = true
        locationLabel.numberOfLines = 1
        locationLabel.adjustsFontSizeToFitWidth = true
        backBtn.transform = CGAffineTransform(rotationAngle: -CGFloat.pi / 2)
        theImage.layer.borderColor = UIColor.black.cgColor
        theImage.layer.borderWidth = 2
        theImage.layer.cornerRadius = 10
    }
}

Answer 1

当您从 userdefaults 获取数组时，它会为您提供 Any 类型数组，因此您需要将其转换为 Int 数组并在使用前检查它是否为零。所以你可以使用这个代码块。

    if let savedDataKey = UserDefaults.standard.array(forKey: "savedDataKey") as? [Int]  {
    print(savedDataKey)
}