当我按下添加时，没有项目被添加到列表中。我的代码出了什么问题？ 我正在尝试使用Core Data制作持久性的购物清单。 请帮我。 在Core Data部分或使用alertController是错误的吗？
import UIKit
import CoreData
class GroceryTableTableViewController: UITableViewController {
var groceries = [NSManagedObject]()
override func viewDidLoad() {
super.viewDidLoad()
self.tableView.register(UITableViewCell.self, forCellReuseIdentifier: "Cell")
}
override func viewWillAppear(_ animated: Bool) {
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let managedContext = appDelegate.persistentContainer.viewContext
super.viewWillAppear(animated)
loadData()
}
func loadData(){
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let managedContext = appDelegate.persistentContainer.viewContext
let request:NSFetchRequest<NSFetchRequestResult> = NSFetchRequest(entityName: "Groceries")
do {
let results = try managedContext.fetch(request)
groceries = results as! [NSManagedObject]
}
catch {
//print(<#T##items: Any...##Any#>)("Error in retrieving Grocery items")
let fetchError = error as NSError
print(fetchError)
}
}
@IBAction func addAction(_ sender: UIBarButtonItem) {
let alertController = UIAlertController(title: "Grocery List", message: "Add Item", preferredStyle: UIAlertControllerStyle.alert)
alertController.addTextField { (textField : UITextField!) -> Void in
}
let addAction = UIAlertAction(title: "Add", style:UIAlertActionStyle.default) { (action: UIAlertAction) -> Void in
func saveItem(itemToSave : String) {
let appDelegate = UIApplication.shared.delegate as! AppDelegate
let managedContext = appDelegate.persistentContainer.viewContext
let entityDescription = NSEntityDescription.entity(forEntityName: "Groceries", in: managedContext)
let item = NSManagedObject(entity: entityDescription!, insertInto: managedContext)
item.setValue(itemToSave, forKey: "item")
do {
try managedContext.save()
self.groceries.append(item)
}
catch {
print("Error in storing to Core Data")
}
}
self.loadData()
}
let cancelAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.default) { (action: UIAlertAction) -> Void in
}
alertController.addAction(addAction)
alertController.addAction(cancelAction)
present(alertController, animated: true, completion: nil)
}
// MARK: - Table view data source
override func numberOfSections(in tableView: UITableView) -> Int {
// #warning Incomplete implementation, return the number of sections
return 1
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// #warning Incomplete implementation, return the number of rows
return groceries.count
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
let item = groceries[indexPath.row]
cell.textLabel?.text = item.value(forKey: "item") as! String
return cell
}
/*
// Override to support conditional editing of the table view.
override func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
// Return false if you do not want the specified item to be editable.
return true
}
*/
/*
// Override to support editing the table view.
override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
if editingStyle == .delete {
// Delete the row from the data source
tableView.deleteRows(at: [indexPath], with: .fade)
} else if editingStyle == .insert {
// Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
}
}
*/
/*
// Override to support rearranging the table view.
override func tableView(_ tableView: UITableView, moveRowAt fromIndexPath: IndexPath, to: IndexPath) {
}
*/
/*
// Override to support conditional rearranging of the table view.
override func tableView(_ tableView: UITableView, canMoveRowAt indexPath: IndexPath) -> Bool {
// Return false if you do not want the item to be re-orderable.
return true
}
*/
/*
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
// Get the new view controller using segue.destinationViewController.
// Pass the selected object to the new view controller.
}
*/
}