卡在重新分配 TableView Cell 属性

Question

我真的希望有人可以帮助我，我已经坚持了2天了。 基本上我正在开发一个应用程序，您可以在其中跟踪您的书籍阅读进度。

HomeViewController 包含一个 TableView，其中列出了您添加的书籍。 它有一个进度条并显示您所在的页面。 AddBookController 用于添加关于委托给 HomeViewController 的书籍的数据，然后列为 TableView Row。 BookDetailController 在您 select 一行时显示，用于更新您所在的页面。 我将提供一些屏幕截图，以便您更好地理解。

一旦您在 BookDetailViewController 中更新 TableView 单元格的“currentPage”属性，我就会陷入困境。 我可以将 updatedPage 发送到 HomeViewController（TableView 所在的位置），但我不知道如何将单元格的值与新值对齐。 我的想法是使用 didSet-observer，但我不知道如何以正确的方式设置它。

这是我的代码

主视图控制器

    class HomeViewController: UIViewController, UITableViewDelegate, UITableViewDataSource, SendingBookDataProtocol {
    
        var updatedPage = String() {
            didSet {    // probably at the wrong place but everything I've tried didn't work
                print(updatedPage)
                tableView?.reloadData()
            }
        }
    
        
        var items = [BookItem]()
        
        var item: BookItem?
    
        override func viewDidLoad() {
            super.viewDidLoad(){
    
            tableView?.delegate = self
            tableView?.dataSource = self
            
            let nib = UINib(nibName: "BookCell", bundle: nil)
            tableView?.register(nib, forCellReuseIdentifier: "BookCell")
    
    }
    
        func sendDataToHomeController(bookEntry item:BookItem) {
            items.append(item)
            tableView.reloadData()
        }
    
        func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
            items.count
        }
    
      func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
          let bookDetailVc = self.storyboard?.instantiateViewController(withIdentifier: "BookDetailView") as? BookDetailViewController
              let item = items[indexPath.row]
              
              let currentPageInt = Float(item.currentPage)!
              let totalPagesInt = Float(item.totalPages)!
              let result = Int(totalPagesInt - currentPageInt)
              let percentageRead = Int((currentPageInt / totalPagesInt) * 100)
              
            bookDetailVc?.lblName = item.title
            bookDetailVc?.lblCurrentPage = Int(Float(item.currentPage)!)
     // ...some more Code. Basically just sending the Data to BookDetailViewController
       
            self.navigationController!.pushViewController(bookDetailVc!, animated: true)
                                         
      }
    
        func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
            let cell = tableView.dequeueReusableCell(withIdentifier: "BookCell", for: indexPath) as! BookCell
            item = items[indexPath.row]
        
            cell.title.text = item?.title
    //... and so on
                cell.pageNumbers.text = "S. " + item!.currentPage + " / " + item!.totalPages //here currentPage needs to be updated
                return cell
            }
        }

BookDetailViewController

class BookDetailViewController: HomeViewController, UIPickerViewDelegate, UIPickerViewDataSource{

    @IBOutlet weak var bookTitle: UILabel!
//...
    @IBOutlet weak var numberPicker: UIPickerView!
    
    var lblName = String()
//...
    var lblCurrentPage = Int()

    override func viewDidLoad() {
        super.viewDidLoad()

        self.numberPicker.delegate = self
        self.numberPicker.dataSource = self
//...
}

    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {

            let valueSelected = pickerData[row] as String
        
        if let homeVc = storyboard?.instantiateViewController(withIdentifier: "getBookData") as? HomeViewController{
            homeVc.updatedPage = valueSelected
            homeVc.tableView?.reloadData()
        }
     }
    }

添加书本控制器

protocol SendingBookDataProtocol {
    func sendDataToHomeController(bookEntry: BookItem)
}

struct BookItem {
    let title,author,currentPage,totalPages:String
    let image: UIImage?
}

class AddBookController: UIViewController, UITextFieldDelegate, UIImagePickerControllerDelegate, UINavigationControllerDelegate {

var delegate: SendingBookDataProtocol? = nil

 @IBAction func buttonSave(_ sender: Any) {

        let bookEntry = BookItem(title: textfieldTitle.text!, author: textfieldAuthor.text!, currentPage: fieldCurrentPage.text!, totalPages: fieldTotalPages.text!, image: bookImage)
        
        self.delegate?.sendDataToHomeController(bookEntry: bookEntry)
                  dismiss(animated: true, completion: nil)
     }
}

// rest should be irrelevant

如果有人能在这方面帮助我，我将不胜感激。 这是屏幕截图

Answer 1

您必须在 BookDetailViewController 中创建一个委托，如下所示：

protocol BookDetailDelegate: AnyObject {
    func updatePage(for bookItem : BookItem)
}


class BookDetailViewController: HomeViewController, UIPickerViewDelegate, UIPickerViewDataSource {
    var item: BookItem
    var delegate: BookDetailDelegate? 
    //...
    }
    
    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
    
       let valueSelected = pickerData[row] as String
       delegate?.updatePage(valueSelected)
     }
}

然后在 HomeViewController 中：

class HomeViewController {
}
//....
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
          let bookDetailVc = self.storyboard?.instantiateViewController(withIdentifier: "BookDetailView") as? BookDetailViewController
              let item = items[indexPath.row]
            bookDetailVc?.item = item
            bookDetailVc?.delegate = self
       
            self.navigationController!.pushViewController(bookDetailVc!, animated: true)
                                         
      }
//.....

extension HomeViewController: BookDetailDelegate {
    func updatePage(for bookItem: BookItem) {
        let index = item.firstIndex(where: {$0.id = bookItem.id}) //here you should have a UUID or something
        item[index] = bookItem
        tableView.performBatchUpdates({
                self.tableView.reloadRows(at: IndexPath(row: index, section: 0, with: .none)}
            }, completion: nil))
    }