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我需要从我的 AppDelegate 获取 de ObjectManagedContext，但是当我尝试它时它不起作用......我不知道为什么......我遵循了大量的教程但它不起作用......这是我的代码：

AppDelegate.h

#import <UIKit/UIKit.h>
@class StopWalletViewController;

@interface StopWalletAppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;

@property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext;
@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;
@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator *persistentStoreCoordinator;

@property (strong, nonatomic) StopWalletViewController *viewController;

@property (strong,nonatomic) UINavigationController *navigationController;

- (void)saveContext;
- (NSURL *)applicationDocumentsDirectory;

@end

AppDelegate.m

#import "StopWalletAppDelegate.h"
#import "StopWalletViewController.h"
@implementation StopWalletAppDelegate

@synthesize managedObjectContext = _managedObjectContext;
@synthesize managedObjectModel = _managedObjectModel;
@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;
@synthesize navigationController = _navigationController;

//Code Auto Generated

// Returns the managed object context for the application.
- (NSManagedObjectContext *)managedObjectContext
{
    if (_managedObjectContext != nil) {
        return _managedObjectContext;
    }

    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];

    if (coordinator != nil) {
        _managedObjectContext = [[NSManagedObjectContext alloc] init];
        [_managedObjectContext setPersistentStoreCoordinator:coordinator];
    }
    return _managedObjectContext;
}

// Returns the managed object model for the application.
- (NSManagedObjectModel *)managedObjectModel
{
    if (_managedObjectModel != nil) {
        return _managedObjectModel;
    }
    NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"StopWallet" withExtension:@"momd"];

    _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];

    return _managedObjectModel;    
}

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
    if (_persistentStoreCoordinator != nil) {
        return _persistentStoreCoordinator;
    }

    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"StopWallet.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.
         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:

         @{NSMigratePersistentStoresAutomaticallyOption:@YES, NSInferMappingModelAutomaticallyOption:@YES}

         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;
}

@end

控制器.m

#import "ExpenseViewController.h"
#import "Expense.h"
#import "ExpenseLocation.h"
#import "StopWalletAppDelegate.h"

@implementation ExpenseViewController

@synthesize editTextDate;
@synthesize editTextLocation;
@synthesize editTextValue;
@synthesize imageViewReceipt;
@synthesize managedObjectContext;

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.navigationItem.title=[NSString stringWithFormat:@"Expense"];
    UIDatePicker *datePicker;
    datePicker = [[UIDatePicker alloc]init];
    [datePicker setDate:[NSDate date]];

    [datePicker setDatePickerMode:UIDatePickerModeDate];
    [datePicker removeTarget:self action:nil forControlEvents:UIControlEventValueChanged];
    [datePicker addTarget:self action:@selector(updateTextFieldDate:) forControlEvents:UIControlEventValueChanged];
    [editTextDate setInputView:datePicker];

    StopWalletAppDelegate *appDelegate = (StopWalletAppDelegate *)[[UIApplication sharedApplication] delegate];
    NSManagedObjectContext* context = appDelegate.managedObjectContext;

    managedObjectContext=context;

}

@end

此代码正在编译，但在运行时不起作用....错误： NSInvalidArgumentException，原因：'无法使用 nil 模型创建 NSPersistentStoreCoordinator'

谁能帮我？

谢谢...

4

2 回答 2

0

尝试将 managedObject 上下文直接分配给 appdelegate。请参见下面的粗线。您能否也分享您的 ExpenseViewController.h 文件。只是想看看您是如何定义 managedObjectContext 属性的。

- (void)viewDidLoad
    {
        [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
        self.navigationItem.title=[NSString stringWithFormat:@"Expense"];
        UIDatePicker *datePicker;
        datePicker = [[UIDatePicker alloc]init];
        [datePicker setDate:[NSDate date]];

        [datePicker setDatePickerMode:UIDatePickerModeDate];
        [datePicker removeTarget:self action:nil forControlEvents:UIControlEventValueChanged];
        [datePicker addTarget:self action:@selector(updateTextFieldDate:) forControlEvents:UIControlEventValueChanged];
        [editTextDate setInputView:datePicker];

        StopWalletAppDelegate *appDelegate = (StopWalletAppDelegate *)[[UIApplication sharedApplication] delegate];
         **self.managedObjectContext= = appDelegate.managedObjectContext;**

    }
于 2013-05-14T12:06:55.900 回答
0

问题应该在 - (NSManagedObjectModel *)managedObjectModel. 检查模型URL

- (NSManagedObjectModel *)managedObjectModel
{
if (_managedObjectModel != nil) {
    return _managedObjectModel;
}
 // Give proper name of your model here
  NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"FailedBankCD" withExtension:@"momd"];
_managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
return _managedObjectModel;
}
于 2013-05-14T12:00:53.457 回答