我试图简单地存储和检索CoreData(我以前用
swift成功的东西).我的数据没有数据,但现在(不知道是什么改变)我没有得到错误,只是没有显示在表格中.我不知道是否存储或检索对象的问题.我已经跟随我在另一个应用程序中尽可能的做了,但似乎有一些根本的事情,我没有得到.这是我有的
我的型号：
import Foundation
import CoreData
@objc(DataModel)
class DataModel: NSManagedObject {
@NSManaged var itemName: String
@NSManaged var quantity: NSNumber
@NSManaged var price: NSNumber
}
在我的tableviewcontroller中,静态单元格用于文本字段,我想保存数据：
import UIKit
import CoreData
class NewItemTableViewController: UITableViewController {
@IBOutlet weak var itemNameTextField: UITextField!
@IBOutlet weak var itemPriceTextField: UITextField!
@IBOutlet weak var itemQuantityTextField: UITextField!
override func viewDidLoad() {
super.viewDidLoad()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
@IBAction func saveButton(sender: AnyObject) {
//CoreData
let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate
let managedContext : NSManagedObjectContext = appDelegate.managedObjectContext!
let entity = NSEntityDescription.entityForName("Item",inManagedObjectContext: managedContext)
var newItem = DataModel(entity: entity!,insertIntoManagedObjectContext: managedContext)
newItem.itemName = itemNameTextField.text
//newItem.price = itemPriceTextField.text
//newItem.quantity = itemQuantityTextField
managedContext.save(nil)
self.navigationController?.popToRootViewControllerAnimated(true)
}
@IBAction func cancelButton(sender: AnyObject) {
self.navigationController?.popToRootViewControllerAnimated(true)
}
在我的tableviewcontroller中,我想在动态单元格中检索数据：
class ItemListTableViewController: UITableViewController {
var items : Array<AnyObject> = []
override func viewDidLoad() {
super.viewDidLoad()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// MARK: - Table view data source
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
// #warning Potentially incomplete method implementation.
// Return the number of sections.
return 1
}
override func tableView(tableView: UITableView,numberOfRowsInSection section: Int) -> Int {
// #warning Incomplete method implementation.
// Return the number of rows in the section.
return items.count
}
override func tableView(tableView: UITableView,cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let CellID: NSString = "cell"
var cell: UITableViewCell = tableView.dequeueReusableCellWithIdentifier(CellID) as UITableViewCell
var data: NSManagedObject = items[indexPath.row] as NSManagedObject
var itemName = data.valueForKey("itemName") as String
var price = data.valueForKey("price") as NSNumber
var quantity = data.valueForKey("quantity") as NSNumber
cell.textLabel!.text! = "\(itemName)"
cell.detailTextLabel!.text! = "Price: \(price) - Quantity: \(quantity)"
return cell
}
任何帮助我可能会错过在这里的某个概念将不胜感激！谢谢.
解决方法
使用核心数据和tableview时,应该使用NSFetchedResultsController.这本质上是从核心数据中检索数据,并通过section和indexPath进行组织,因此可以方便地将其设置为tableView的数据源.以下是符合NSFetchedResultsControllerDelegate的潜在UITableViewController的完整实现：
import Foundation
import UIKit
import CoreData
class HomeViewController: UITableViewController,NSFetchedResultsControllerDelegate {
let managedObjectContext: NSManagedObjectContext? = (UIApplication.sharedApplication().delegate as? AppDelegate)?.managedObjectContext
var fetchedResultsController: NSFetchedResultsController?
override func viewDidLoad() {
super.viewDidLoad()
fetchedResultsController = NSFetchedResultsController(fetchRequest: allEmployeesFetchRequest(),managedObjectContext: managedObjectContext!,sectionNameKeyPath: nil,cacheName: nil)
fetchedResultsController?.delegate = self
fetchedResultsController?.performFetch(nil)
}
func allEmployeesFetchRequest() -> NSFetchRequest {
var fetchRequest = NSFetchRequest(entityName: "Employee")
let sortDescriptor = NSSortDescriptor(key: "nameLast",ascending: true)
fetchRequest.predicate = nil
fetchRequest.sortDescriptors = [sortDescriptor]
fetchRequest.fetchBatchSize = 20
return fetchRequest
}
//MARK: UITableView Data Source and Delegate Functions
override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
return fetchedResultsController?.sections?.count ?? 0
}
override func tableView(tableView: UITableView,numberOfRowsInSection section: Int) -> Int {
return fetchedResultsController?.sections?[section].numberOfObjects ?? 0
}
override func tableView(tableView: UITableView,cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCellWithIdentifier("HomeCell",forIndexPath: indexPath) as UITableViewCell
if let cellContact = fetchedResultsController?.objectAtIndexPath(indexPath) as? Employee {
cell.textLabel?.text = "\(cellContact.nameLast),\(cellContact.nameFirst)"
}
return cell
}
//MARK: NSFetchedResultsController Delegate Functions
func controller(controller: NSFetchedResultsController,didChangeSection sectionInfo: NSFetchedResultsSectionInfo,atIndex sectionIndex: Int,forChangeType type: NSFetchedResultsChangeType) {
switch type {
case NSFetchedResultsChangeType.Insert:
tableView.insertSections(NSIndexSet(index: sectionIndex),withRowAnimation: UITableViewRowAnimation.Fade)
break
case NSFetchedResultsChangeType.Delete:
tableView.deleteSections(NSIndexSet(index: sectionIndex),withRowAnimation: UITableViewRowAnimation.Fade)
break
case NSFetchedResultsChangeType.Move:
break
case NSFetchedResultsChangeType.Update:
break
default:
break
}
}
override func tableView(tableView: UITableView,commitEditingStyle editingStyle: UITableViewCellEditingStyle,forRowAtIndexPath indexPath: NSIndexPath) {
if editingStyle == .Delete {
}
switch editingStyle {
case .Delete:
managedObjectContext?.deleteObject(fetchedResultsController?.objectAtIndexPath(indexPath) as Employee)
managedObjectContext?.save(nil)
case .Insert:
break
case .None:
break
}
}
func controller(controller: NSFetchedResultsController,didChangeObject anObject: AnyObject,atIndexPath indexPath: NSIndexPath?,forChangeType type: NSFetchedResultsChangeType,newIndexPath: NSIndexPath?) {
switch type {
case NSFetchedResultsChangeType.Insert:
tableView.insertRowsAtIndexPaths(NSArray(object: newIndexPath!),withRowAnimation: UITableViewRowAnimation.Fade)
break
case NSFetchedResultsChangeType.Delete:
tableView.deleteRowsAtIndexPaths(NSArray(object: indexPath!),withRowAnimation: UITableViewRowAnimation.Fade)
break
case NSFetchedResultsChangeType.Move:
tableView.deleteRowsAtIndexPaths(NSArray(object: indexPath!),withRowAnimation: UITableViewRowAnimation.Fade)
tableView.insertRowsAtIndexPaths(NSArray(object: newIndexPath!),withRowAnimation: UITableViewRowAnimation.Fade)
break
case NSFetchedResultsChangeType.Update:
tableView.cellForRowAtIndexPath(indexPath!)
break
default:
break
}
}
func controllerWillChangeContent(controller: NSFetchedResultsController) {
tableView.beginUpdates()
}
func controllerDidChangeContent(controller: NSFetchedResultsController) {
tableView.endUpdates()
}
}
