问题描述
我想从AddViewController更新itemViewController中的行名。在我的代码中，我将包含名称和说明的item对象传递给了我的AddViewController并更改了值，但是行名称从未更新。
我环顾了互联网，发现了有关所谓的委托模式的信息。我只是不确定如何实现该模式。谢谢您的提前帮助。
// ItemsViewController.swift
// Project 3-Todo
//
// Created by Gracias Claude on 10/9/20.
//
import UIKit
class ItemsViewController : UITableViewController {
var itemStore: ItemStore!
@IBAction func addNewItem(_ sender: UIButton) {
// Create a new item and add it to the store
let newItem = itemStore.createItem()
// figure out where that item is in the array
if let index = itemStore.allItems.firstIndex(of: newItem) {
let indexPath = IndexPath(row: index,section: 0)
// Insert this new row into the table
tableView.insertRows(at: [indexPath],with: .automatic)
}
}
@IBAction func toggleEditingMode(_ sender: UIButton) {
// If you are currently in editing mode...
if isEditing {
// Change text of button to inform user of state
sender.setTitle("Edit",for: .normal)
// Turn off editing mode
setEditing(false,animated: true)
} else {
// Change text of button to inform user of state
sender.setTitle("Done",for: .normal)
// Enter editing mode
setEditing(true,animated: true)
}
}
override func tableView(_ tableView: UITableView,numberOfRowsInSection section: Int) -> Int {
return itemStore.allItems.count
}
// returning table view cell
override func tableView(_ tableView: UITableView,cellForRowAt indexPath: IndexPath) -> UITableViewCell {
// Get a new or recycled cell
let cell = tableView.dequeueReusableCell(withIdentifier: "UITableViewCell",for: indexPath)
// Set the text on the cell with the description of the item
// that is at the nth index of items,where n = row this cell
// will appear in on the table view
let item = itemStore.allItems[indexPath.row]
cell.textLabel?.text = item.name
cell.detailTextLabel?.text = "\(item.dateCreated)"
return cell
}
override func tableView(_ tableView: UITableView,commit editingStyle: UITableViewCell.EditingStyle,forRowAt indexPath: IndexPath) {
// If the table view is asking to commit a delete command...
if editingStyle == .delete {
let item = itemStore.allItems[indexPath.row]
// Remove the item from the store
itemStore.removeItem(item)
// Also remove that row from the table view with an animation
tableView.deleteRows(at: [indexPath],with: .automatic)
}
}
override func tableView(_ tableView: UITableView,moveRowAt sourceIndexPath: IndexPath,to destinationIndexPath: IndexPath) {
// Update the model
itemStore.moveItem(from: sourceIndexPath.row,to: destinationIndexPath.row)
}
override func prepare(for segue: UIStoryboardSegue,sender: Any?) {
// If the triggered segue is the "showItem" segue
switch segue.identifier {
case "showItem":
print("Hello World")
// figure out which row was just tapped
if let row = tableView.indexPathForSelectedRow?.row {
// Get the item associated with this row and pass it along
let item = itemStore.allItems[row]
let detailViewController
= segue.destination as! DetailsViewController
detailViewController.item = item
}
break;
case "addItem":
let row = tableView.indexPathForSelectedRow?.row ?? 0
// // Get the item associated with this row and pass it along
let item = itemStore.allItems[row]
let addViewController
= segue.destination as! AddViewController
addViewController.item = item
// }
break;
default:
preconditionFailure("Unexpected segue identifier.")
}
}
}
//AddViewController
//
// AddViewController.swift
// Project 3-Todo
//
// Created by Gracias Claude on 10/9/20.
//
import UIKit
class AddViewController : UIViewController {
var item: Item!;
@IBOutlet weak var itemNameField: UITextField!
@IBOutlet weak var priorityField: UITextField!
@IBOutlet weak var descriptionField: UITextField!
@IBAction func submitItem(_ sender: UIButton) {
//how to update the existing Row name
item.name = itemNameField.text ?? "Default Text"
item.description = descriptionField.text ?? "default Description"
return;
}
}
解决方法
据我了解，您正在将数据从ItemViewController传递到AddViewController。然后，您可以从AddViewController更改该值，并希望该更改反映回ItemViewController。
如果是这种情况，则必须将修改后的数据传回给ItemViewController，并且有很多方法可以做到这一点。
最简单的方法（我认为这不是最佳实践）是在ItemViewController内创建一个函数来捕获新更改。
func captureModified(itemStore: ItemStore) {
self.itemStore = itemStore
}
接下来，当您从ItemViewController过渡到AddViewController时，请在ItemViewController中创建AddViewController的实例，并在从ItemViewController过渡到AddViewController时对其进行初始化。 class AddViewController: UIViewController {
weak var itemViewController: ItemViewController?
}
。
ItemViewController从AddViewController到let addViewController = segue.destination as! AddViewController
addViewController.itemViewController = self
的过渡
deinit最后，当您过渡回来时；您可以在AddViewController方法中执行此操作，也可以在deinit {
itemViewController.captureModified(itemStore: itemStore)
}
方法中创建自己的back方法。
captureModified(_:)这是做事的最简单方法。最安全和最佳的做法是将ItemViewController方法包装在协议中，并创建该协议的实例，而不是整个print类。让我知道您是否愿意这样做，我可以实施。或者在时间允许的情况下，不管将来的读者如何，我都会把它放进去。
我向String的新segue回到了AddViewController
itemViewController在 switch segue.identifier {
case "added":
let itemsViewController = segue.destination as! ItemsViewController
itemsViewController.itemStore = itemStore
default:
preconditionFailure("Unexpected segue identifier.")
中保持单元格索引的轨迹
itemsViewController并向 @IBAction func addNewItem(_ sender: UIButton) {
// Create a new item and add it to the store
let newItem = itemStore.createItem()
// Figure out where that item is in the array
if let index = itemStore.allItems.firstIndex(of: newItem) {
let indexPath = IndexPath(row: index,section: 0)
self.row = index
// Insert this new row into the table
tableView.insertRows(at: [indexPath],with: .automatic)
}
}
传递了要更新的正确行，以便AddViewController知道正在更新的那一行
ItemViewController我还在
let row = self.row
// // Get the item associated with this row and pass it along
let item = itemStore.allItems[row]
let itemStore = self.itemStore;
let addViewController
= segue.destination as! AddViewController
addViewController.item = item
addViewController.itemStore = itemStore
addViewController.row = self.row;
// }
break;
default:
preconditionFailure("Unexpected segue identifier.")
}
的顶部添加了它，以拥有AddViewController itemViewController