Core data 核心数据未解析错误（null），（null）

我昨天安装并运行了这个应用程序的一个版本。我重新开始是因为我想练习并添加一些功能。但今天，我无法完成为实体添加新对象的最基本任务。在尝试保存时，我不断遇到相同的错误：

未解决的错误（null），（null）

大部分早期代码都是从工作应用程序中复制和粘贴的。当这不起作用时，我创建了一个新项目并重新键入了所有代码。没有骰子。因此，我删除了所有派生数据，删除了应用程序的所有早期版本，重置了模拟器，关闭了Xcode，重新启动了我的机器，创建了一个新项目，并重新键入了这四个类。但我还是犯了同样的错误。我的模型中没有强制属性。我在这里把头撞在墙上。有什么想法吗？以下是我正在使用的类的代码：

//  PublisherTableViewController.h

#import <UIKit/UIKit.h>
#import "Publisher.h"


@interface PublisherTableViewController : UITableViewController <NSFetchedResultsControllerDelegate, PublisherAddDelegate>{
    @private

    NSFetchedResultsController *fetchedResultsController;
    NSManagedObjectContext *managedObjectContext;



}

@property (strong, nonatomic) NSFetchedResultsController *fetchedResultsController;
@property (strong, nonatomic) NSManagedObjectContext *managedObjectContext;


- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath;

//PublisherTableViewController.h
#进口
#导入“Publisher.h”
@接口PublisherTableViewController:UITableViewController{
@私人的
NSFetchedResultsController*fetchedResultsController；
NSManagedObjectContext*managedObjectContext；
}
@属性（强，非原子）NSFetchedResultsController*fetchedResultsController；
@属性（强，非原子）NSManagedObjectContext*managedObjectContext；
-（void）configureCell:（UITableViewCell*）单元格atIndexPath:（NSIndexPath*）indexPath；

//PublisherTableViewController.m

#import "AddPublisherTableViewController.h"
#import "PublisherTableViewController.h"
#import "AppDelegate.h"


@interface PublisherTableViewController ()

@end

@implementation PublisherTableViewController
@synthesize fetchedResultsController, managedObjectContext;

- (id)initWithStyle:(UITableViewStyle)style
{
    self = [super initWithStyle:style];
    if (self) {
        // Custom initialization
    }
    return self;
}


-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([[segue identifier] isEqualToString:@"AddPublisherSegue"]) {
        AddPublisherTableViewController *addPublisherController = (AddPublisherTableViewController *) [[segue destinationViewController] topViewController];
        addPublisherController.delegate = self;

        Publisher *newPublisher = [NSEntityDescription insertNewObjectForEntityForName:@"Publisher" inManagedObjectContext:self.managedObjectContext];
        addPublisherController.publisher = newPublisher;
    }
}

-(void)publisherAddViewController:(AddPublisherTableViewController *)publisherAddViewController didAddPublisher:(Publisher *)publisher
{
    [self dismissModalViewControllerAnimated:YES];
}

- (void)viewDidLoad
{

    if (managedObjectContext == nil) 
    { 
        managedObjectContext = [(AppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext]; 
        //NSLog(@"After managedObjectContext: %@",  managedObjectContext);
    }

    NSError *error = nil;
    if (![[self fetchedResultsController] performFetch:&error ]) {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    }

    [super viewDidLoad];

    // Uncomment the following line to preserve selection between presentations.
    // self.clearsSelectionOnViewWillAppear = NO;

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem;
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{

    // Return the number of sections.
    return [[self.fetchedResultsController sections]count];


}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{

    // Return the number of rows in the section.

    id<NSFetchedResultsSectionInfo> sectionInfo = [[self.fetchedResultsController sections] objectAtIndex:section];

    return [sectionInfo numberOfObjects];
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"PublisherCell";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

    // Configure the cell...

    [self configureCell:cell atIndexPath:indexPath];

    return cell;
}

-(void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath
{
    Publisher *publisherForCell = (Publisher *)[fetchedResultsController objectAtIndexPath:indexPath];
    cell.textLabel.text = [NSString stringWithFormat:@"%@ %@",publisherForCell.firstName, publisherForCell.lastName];
    cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
}

/*
// 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;
}
*/

/*
// Override to support editing the table view.
- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        // Delete the row from the data source
        [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
    }   
    else if (editingStyle == UITableViewCellEditingStyleInsert) {
        // 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.
- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath
{
}
*/

/*
// Override to support conditional rearranging of the table view.
- (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Return NO if you do not want the item to be re-orderable.
    return YES;
}
*/

#pragma mark - Table view delegate

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Navigation logic may go here. Create and push another view controller.
    /*
     <#DetailViewController#> *detailViewController = [[<#DetailViewController#> alloc] initWithNibName:@"<#Nib name#>" bundle:nil];
     // ...
     // Pass the selected object to the new view controller.
     [self.navigationController pushViewController:detailViewController animated:YES];
     */
}

- (NSFetchedResultsController *)fetchedResultsController {
    // Set up the fetched results controller if needed.


    if (fetchedResultsController == nil) {

        // Create the fetch request for the entity.
        NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
        // Edit the entity name as appropriate.
        NSEntityDescription *entity = [NSEntityDescription entityForName:@"Publisher" inManagedObjectContext:managedObjectContext];
        [fetchRequest setEntity:entity];

        // Edit the sort key as appropriate.
        NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"lastName" ascending:YES];
        NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];

        [fetchRequest setSortDescriptors:sortDescriptors];

        // Edit the section name key path and cache name if appropriate.
        // nil for section name key path means "no sections".
        NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:nil cacheName:@"Root"];
        aFetchedResultsController.delegate = self;
        self.fetchedResultsController = aFetchedResultsController;

        //        [aFetchedResultsController release];
        //        [fetchRequest release];
        //        [sortDescriptor release];
        //        [sortDescriptors release];
    }

    return fetchedResultsController;
}    


/**
 Delegate methods of NSFetchedResultsController to respond to additions, removals and so on.
 */

- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
    // The fetch controller is about to start sending change notifications, so prepare the table view for updates.
    [self.tableView beginUpdates];
}


- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath {
    UITableView *tableView = self.tableView;

    switch(type) {
        case NSFetchedResultsChangeInsert:
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeUpdate:
            [self configureCell:(UITableViewCell *)[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
            break;

        case NSFetchedResultsChangeMove:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}


- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {
    switch(type) {
        case NSFetchedResultsChangeInsert:
            [self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}


- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
    // The fetch controller has sent all current change notifications, so tell the table view to process all updates.
    [self.tableView endUpdates];
}


@end

#import "AddPublisherTableViewController.h"

@interface AddPublisherTableViewController ()

@end

@implementation AddPublisherTableViewController

@synthesize delegate, firstName, lastName, publisher;

- (id)initWithStyle:(UITableViewStyle)style
{
    self = [super initWithStyle:style];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    // Uncomment the following line to preserve selection between presentations.
    // self.clearsSelectionOnViewWillAppear = NO;

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem;
}


-(IBAction)savePublisher
{
    publisher.firstName = firstName.text;
    publisher.lastName = lastName.text;

    NSError *error = nil;

    if (![publisher.managedObjectContext save:&error]) {
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    }

    [self.delegate publisherAddViewController:self didAddPublisher:publisher];

}

-(IBAction)cancel
{
    if (publisher.firstName == NULL) {
        [publisher.managedObjectContext deleteObject:publisher];

        NSError *error = nil;

        if (![publisher.managedObjectContext save:&error]) {
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    }
        [self.delegate publisherAddViewController:self didAddPublisher:nil];
    }else {
        [self.delegate publisherAddViewController:self didAddPublisher:publisher];
    }
}    

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

@end
    id<PublisherAddDelegate> delegate;

}

@property (nonatomic, strong) Publisher *publisher;
@property (nonatomic, strong) IBOutlet UITextField *firstName;
@property (nonatomic, strong) IBOutlet UITextField *lastName;
@property (nonatomic, strong) id<PublisherAddDelegate> delegate;

-(IBAction)savePublisher;
-(IBAction)cancel;

@end

@protocol PublisherAddDelegate <NSObject>

-(void)publisherAddViewController:(AddPublisherTableViewController *)publisherAddViewController didAddPublisher:(Publisher *)publisher;

@end

#import "AddPublisherTableViewController.h"
#import "PublisherTableViewController.h"
#import "AppDelegate.h"


@interface PublisherTableViewController ()

@end

@implementation PublisherTableViewController
@synthesize fetchedResultsController = mFetchedResultsController
@synthesize managedObjectContext = mManagedObjectContext;

...

#导入“AddPublisherTableViewController.h”
#导入“PublisherTableViewController.h”
#导入“AppDelegate.h”
@接口PublisherTableViewController（）
@结束
@实现PublisherTableViewController
@综合fetchedResultsController、managedObjectContext；
-（id）initWithStyle:（UITableViewStyle）样式
{
self=[super initWithStyle:style]；
如果（自我）{
//自定义初始化
}
回归自我；
}
-（void）prepareForSegue:（UIStoryboardSegue*）segue发送方：（id）发送方
{
if（[[segue identifier]IsequalString:@“addPublishersgue”]）{
AddPublisherTableViewController*addPublisherController=（AddPublisherTableViewController*）[[segue destinationViewController]topViewController]；
addPublisherController.delegate=self；
Publisher*newPublisher=[NSEntityDescription insertNewObjectForEntityForName:@“Publisher”在managedObjectContext:self.managedObjectContext]中；
addPublisherController.publisher=newPublisher；
}
}
-（void）PublisherADVIEWController:（添加PublisherTableViewController*）PublisherADVIEWController didAddPublisher:（发布者*）发布者
{
[自我解散Modalviewcontrolleranimated:是]；
}
-（无效）viewDidLoad
{
if（managedObjectContext==nil）
{ 
managedObjectContext=[（AppDelegate*）[[UIApplication sharedApplication]委托]managedObjectContext]；
//NSLog（@“在managedObjectContext之后：%@”，managedObjectContext）；
}
n错误*错误=nil；
如果（！[[self-fetchedResultsController]性能检测：&错误]）{
NSLog（@“未解决的错误%@，%@”，错误，[error userInfo]）；
}
[超级视图下载]；
//取消对下一行的注释以保留演示文稿之间的选择。
//self.clearselectiononviewwillappear=否；
//取消对以下行的注释，以在此视图控制器的导航栏中显示编辑按钮。
//self.navigationItem.rightBarButtonItem=self.editButtonItem；
}
-（无效）视图卸载
{
[超级视频下载]；
//释放主视图的所有保留子视图。
//例如，self.myOutlet=nil；
}
-（布尔）应自动旋转指针面定向：（UIInterfaceOrientation）interfaceOrientation
{
返回（interfaceOrientation==UIInterfaceOrientationGraphic）；
}
#pragma标记-表视图数据源
-（NSInteger）表格视图中的节数：（UITableView*）表格视图
{
//返回节数。
返回[[self.fetchedResultsController节]计数]；
}
-（NSInteger）表视图：（UITableView*）表视图行数节：（NSInteger）节
{
//返回节中的行数。
id sectionInfo=[[self.fetchedResultsController节]objectAtIndex:section]；
返回[sectionInfo numberOfObjects]；
}
-（UITableViewCell*）tableView:（UITableView*）tableView cellForRowAtIndexPath:（NSIndexPath*）indexPath
{
静态NSString*CellIdentifier=@“PublisherCell”；
UITableViewCell*单元格=[tableView dequeueReusableCellWithIdentifier:CellIdentifier]；
//配置单元格。。。
[self-configureCell:cell-atIndexPath:indexPath]；
返回单元；
}
-（void）configureCell:（UITableViewCell*）单元格atIndexPath:（NSIndexPath*）indexPath
{
Publisher*Publisher-forcell=（Publisher*）[fetchedResultsController对象索引路径：indexPath]；
cell.textLabel.text=[NSString stringWithFormat:@“%@%@”，publisherForCell.firstName，publisherForCell.lastName]；
cell.accessoryType=UITableViewCellAccessoryDisclosureIndicator；
}
/*
//替代以支持表视图的条件编辑。
-（BOOL）tableView:（UITableView*）tableView caneditrowatinexpath:（nsindepath*）indepath
{
//如果不希望指定的项可编辑，则返回“否”。
返回YES；
}
*/
/*
//替代以支持编辑表格视图。
-（void）tableView:（UITableView*）tableView提交的编辑样式：（UITableViewCellEditingStyle）行的编辑样式索引路径：（NSIndexPath*）索引路径
{
如果（editingStyle==UITableViewCellEditingStyleDelete）{
//从数据源中删除该行
[tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath]和RowAnimation:UITableViewRowAnimationFade]；
}   
else if（editingStyle==UITableViewCellEditingStyleInsert）{
//创建相应类的新实例，将其插入数组，并向表视图添加新行
}   
}
*/
/*
//替代以支持重新排列表视图。
-（void）tableView:（UITableView*）tableView移动rowatinexpath:（nsindepath*）从indepath到indepath:（nsindepath*）到indepath
{
}
*/
/*
//超越支持
//  PublisherTableViewController.h

#import <UIKit/UIKit.h>
#import "Publisher.h"


@interface PublisherTableViewController : UITableViewController <NSFetchedResultsControllerDelegate, PublisherAddDelegate>{
    @private

    NSFetchedResultsController *mFetchedResultsController;
    NSManagedObjectContext *mManagedObjectContext;
}

@property (strong, nonatomic) NSFetchedResultsController *fetchedResultsController;
@property (strong, nonatomic) NSManagedObjectContext *managedObjectContext;

- (void)configureCell:(UITableViewCell *)cell atIndexPath:(NSIndexPath *)indexPath;

#import "AddPublisherTableViewController.h"
#import "PublisherTableViewController.h"
#import "AppDelegate.h"


@interface PublisherTableViewController ()

@end

@implementation PublisherTableViewController
@synthesize fetchedResultsController = mFetchedResultsController
@synthesize managedObjectContext = mManagedObjectContext;

...