我正在開發一個應用程式，您可以在其中跟蹤您的書籍閱讀進度。
HomeViewController 包含一個 TableView，其中列出了您添加的書籍。它有一個進度條并顯示您所在的頁面。AddBookController 用于添加關于委托給 HomeViewController 的書籍的資料，然后列為 TableView Row。BookDetailController 在您選擇 Row 時顯示，用于更新您所在的 Page。我會提供一些截圖。
一旦您在 BookDetailViewController 中更新 TableView 單元格的“currentPage”屬性，我就會陷入困境。我可以將 updatedPage 發送到 HomeViewController（TableView 所在的位置），但我不知道如何將單元格的值與新值對齊。我的想法是使用 didSet-observer，但我不知道如何以正確的方式設定它。
這是我的代碼：
主視圖控制器
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()
}
}
}
添加書本控制器
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
以下是截圖：
uj5u.com熱心網友回復：
您必須在 BookDetailViewController 中創建一個委托，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))
}
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