为什么核心数据不能获取我的数据？ [英] Why Isn't Core Data Fetching My Data?
问题描述
在重新启动时不会提取实体属性的我的数据，也不会在退出之前保存（可能是两种情况之一）。底线是，重新启动时数据不会显示在表中。我想我可能需要整合我的核心数据方法或将它们移动到应用程序委托文件。
My data for for an entity's attribute is not being fetched upon restart or not being saved before quitting (could be either case). The bottom line is, the data is not showing up in the table upon restart. I think I may need to consolidate my core data methods or move them to the app delegate file instead.
我认为我的核心数据代码都搞乱了，任何人都可以帮助修理它？
让我知道如果你需要任何额外的代码来看看从appdelegate.m等
这里是我的视图控制器的代码：
I think my core data code is all messed up, can anyone help fix it? Let me know if you need any additional code to look at from the appdelegate.m etc. Here is the code for my View Controller:
#import "RoutineTableViewController.h"
#import "AlertPrompt.h"
#import "Routine.h"
#import "CurlAppDelegate.h"
@implementation RoutineTableViewController
@synthesize tableView;
@synthesize eventsArray;
@synthesize managedObjectContext;
- (void)dealloc
{
[managedObjectContext release];
[eventsArray release];
[super dealloc];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
}
- (NSManagedObjectContext *) managedObjectContext {
if (managedObjectContext != nil) {
return managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil) {
managedObjectContext = [[NSManagedObjectContext alloc] init];
[managedObjectContext setPersistentStoreCoordinator: coordinator];
}
return managedObjectContext;
}
-(void)addEvent
{
Routine *routine = (Routine *)[NSEntityDescription insertNewObjectForEntityForName:@"Routine" inManagedObjectContext:managedObjectContext];
CurlAppDelegate *curlAppDelegate = [[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [curlAppDelegate managedObjectContext];
NSManagedObject *newRoutineEntry;
newRoutineEntry = [NSEntityDescription insertNewObjectForEntityForName:@"Routine" inManagedObjectContext:context];
NSError *error = nil;
if (![managedObjectContext save:&error]) {
// Handle the error.
}
[eventsArray insertObject:routine atIndex:0];
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:0 inSection:0];
[self.tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
[self.tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:0 inSection:0] atScrollPosition:UITableViewScrollPositionTop animated:YES];
}
#pragma mark - View lifecycle
- (void)viewDidLoad
{
CurlAppDelegate *curlAppDelegate = [[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [curlAppDelegate managedObjectContext];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Routine" inManagedObjectContext:context];
[request setEntity:entity];
NSError *error = nil;
NSMutableArray *mutableFetchResults = [[context executeFetchRequest:request error:&error] mutableCopy];
if (mutableFetchResults == nil) {
// Handle the error.
}
[self setEventsArray:mutableFetchResults];
[mutableFetchResults release];
[request release];
UIBarButtonItem * addButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(showPrompt)];
[self.navigationItem setLeftBarButtonItem:addButton];
[addButton release];
UIBarButtonItem *editButton = [[UIBarButtonItem alloc]initWithTitle:@"Edit" style:UIBarButtonItemStyleBordered target:self action:@selector(toggleEdit)];
self.navigationItem.rightBarButtonItem = editButton;
[editButton release];
[super viewDidLoad];
}
-(void)toggleEdit
{
[self.tableView setEditing: !self.tableView.editing animated:YES];
if (self.tableView.editing)
[self.navigationItem.rightBarButtonItem setTitle:@"Done"];
else
[self.navigationItem.rightBarButtonItem setTitle:@"Edit"];
}
-(void)showPrompt
{
AlertPrompt *prompt = [AlertPrompt alloc];
prompt = [prompt initWithTitle:@"Add Workout Day" message:@"\n \n Please enter title for workout day" delegate:self cancelButtonTitle:@"Cancel" okButtonTitle:@"Add"];
[prompt show];
[prompt release];
}
- (void)alertView:(UIAlertView *)alertView willDismissWithButtonIndex:(NSInteger)buttonIndex
{
if (buttonIndex != [alertView cancelButtonIndex])
{
NSString *entered = [(AlertPrompt *)alertView enteredText];
if(eventsArray && entered)
{
[eventsArray addObject:entered];
[tableView reloadData];
}
}
}
- (void)viewDidUnload
{
self.eventsArray = nil;
[super viewDidUnload];
}
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
}
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
}
- (void)viewWillDisappear:(BOOL)animated
{
[super viewWillDisappear:animated];
}
- (void)viewDidDisappear:(BOOL)animated
{
[super viewDidDisappear:animated];
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
// Return YES for supported orientations
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}
#pragma mark - Table view data source
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return [eventsArray count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = @"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellEditingStyleDelete reuseIdentifier:CellIdentifier] autorelease];
cell.textLabel.text = [self.eventsArray objectAtIndex:indexPath.row];
return cell;
}
// Override to support conditional editing of the table view.
- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
// Return NO if you do not want the specified item to be editable.
return YES;
}
-(void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
if (editingStyle == UITableViewCellEditingStyleDelete) {
// Delete the managed object at the given index path.
NSManagedObject *eventToDelete = [eventsArray objectAtIndex:indexPath.row];
[managedObjectContext deleteObject:eventToDelete];
// Update the array and table view.
[eventsArray removeObjectAtIndex:indexPath.row];
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:YES];
// Commit the change.
NSError *error = nil;
if (![managedObjectContext save:&error]) {
// Handle the error.
}
}
}
@end
这里是数据模型：
And here is the data model:
编辑：
添加PersisentStoreCoordinater方法（来自应用程式委托）：
Added PersisentStoreCoordinater Method (From App Delegate):
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
if (__persistentStoreCoordinator != nil)
{
return __persistentStoreCoordinator;
}
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"Curl.sqlite"];
NSError *error = nil;
__persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error])
{
/*
Replace this implementation with code to handle the error appropriately.
abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
Typical reasons for an error here include:
* The persistent store is not accessible;
* The schema for the persistent store is incompatible with current managed object model.
Check the error message to determine what the actual problem was.
If the persistent store is not accessible, there is typically something wrong with the file path. Often, a file URL is pointing into the application's resources directory instead of a writeable directory.
If you encounter schema incompatibility errors during development, you can reduce their frequency by:
* Simply deleting the existing store:
[[NSFileManager defaultManager] removeItemAtURL:storeURL error:nil]
* Performing automatic lightweight migration by passing the following dictionary as the options parameter:
[NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];
Lightweight migration will only work for a limited set of schema changes; consult "Core Data Model Versioning and Data Migration Programming Guide" for details.
*/
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return __persistentStoreCoordinator;
}
推荐答案
修复此问题：
- 删除RoutineViewController中对managedObjectContext等的所有引用。
- 每当您需要参考（例如在 AddEvent 方法中）时，请从您的委托中引用适当的对象 当这变得更复杂时，您可能需要一个DataManager类来处理所有您的CoreData对象。使它成为一个单例，你将能够在任何类中引用它。为了获取显示的对象，你可以在这个类中创建必要的方法来检索这些对象在NSMutableArray
- Remove all references to managedObjectContext, etc. in your RoutineViewController. Only reference the CoreData classes / properties from your AppDelegate.
- Whenever you need a reference (say in your AddEvent method) reference the appropriate objects from your delegate (see code below)
When this gets more complex, you'll probably want a DataManager class that handles ALL your CoreData objects. Make it a Singleton, and you'll be able to reference it in any class. For fetching objects for display, you can then create the necessary methods in this class to retrieve these objects in a NSMutableArray
CurlAppDelegate * curlAppDelegate = [[UIApplication sharedApplication] delegate]; NSManagedObjectContext * context = [curlAppDelegate managedObjectContext];
CurlAppDelegate *curlAppDelegate = [[UIApplication sharedApplication] delegate]; NSManagedObjectContext *context = [curlAppDelegate managedObjectContext];
例程* routine =（Routine *）[NSEntityDescription insertNewObjectForEntityForName：@RoutineinManagedObjectContext：context];
Routine *routine = (Routine *)[NSEntityDescription insertNewObjectForEntityForName:@"Routine" inManagedObjectContext:context];
查看您现在如何使用上下文从AppDelegate 而不是本地？这很重要，因为你的应用程序会在初始化时将你的xdatamodel从你的Bundle链接到你的AppDelegate。
See how you're now using the context from your AppDelegate and not locally? This is important, because your app will link your xdatamodel from your Bundle into your AppDelegate on initialization.
如果你担心数据没有被保存或覆盖，请查看您的AppDelegate的 - （NSPersistentStoreCoordinator *）persistentStoreCoordinator
If you're concerned about the data not being saved, or overwritten, check out your AppDelegate's - (NSPersistentStoreCoordinator *)persistentStoreCoordinator
这是设置在您退出并进入应用程序时链接到您的存储数据库的地方。这是你的AppDelegate中加载Curl.sqlite文件中的代码（修改）：
That's where the setup happens to link to your stored database when you exit and enter the app. Here's your code (modified) in your AppDelegate that loads in the Curl.sqlite file :
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator{
if (__persistentStoreCoordinator != nil)
{
return __persistentStoreCoordinator;
}
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"Curl.sqlite"];
NSError *error = nil;
__persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error])
{
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return __persistentStoreCoordinator;
}
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