Question

我正在尝试重置使用Core Data的应用程序，为此，我编写了以下代码

- (void) resetApplicationModel
{
//    NSError *error;
    NSError *error;
    // retrieve the store URL
    NSURL * storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"abc.sqlite"];
    // lock the current context
    [self.managedObjectContext lock];

   [self.managedObjectContext reset];//to drop pending changes
    //delete the store from the current managedObjectContext
    if ([[self.managedObjectContext persistentStoreCoordinator] removePersistentStore:[[[self.managedObjectContext persistentStoreCoordinator] persistentStores] lastObject] error:&error])
    {
        // remove the file containing the data
        if([[NSFileManager defaultManager] removeItemAtURL:storeURL error:&error])
        {
            //recreate the store like in the appDelegate method
            if([[self.managedObjectContext persistentStoreCoordinator] addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error] == nil)
            {
                NSLog( @"could not create new persistent store at %@ - %@", [storeURL absoluteString], [error localizedDescription]);
            }
        }
        else
        {
            NSLog( @"could not remove the store URL at %@ - %@", [storeURL absoluteString], [error localizedDescription]);
        }

    }
    else
    {
        NSLog( @"could not remove persistent store - %@", [error localizedDescription]);
    }
    [self.managedObjectContext unlock];

      __managedObjectContext = nil;

    [self managedObjectContext];

    _rootViewController.controller = nil;//Make NSFetchResultsController nil;

}

此代码在ios 6.1模拟器上工作正常并且没有问题，但是当我在运行iOS 6.1.3的iphone 4上检查时，持久性文件未被删除，我收到错误

＆＃34;无法删除文件中的商店网址：//localhost/var/mobile/Applications/147E198E-FAB9-46EA-BE4B-4411AFA013FB/Documents/abc.sqlite - 操作无法执行完成。（可可错误4。）＆＃34;

但所有数据都被删除了，现在当我尝试在coreData中添加新数据时，我收到错误说

＆＃34;由于未捕获的异常终止应用程序＆＃39; NSInternalInconsistencyException＆＃39;，原因：＆＃39;此NSPersistentStoreCoordinator没有持久存储。它无法执行保存操作。＆＃39;＆＃34;

请帮帮我们

此致兰吉特

Answer 1

在NSManagedObjectContext上创建一个类别，然后实现：

- (BOOL)deleteAllObjectsForEntityName:(NSString *)entity withError:(NSError *__autoreleasing *)error {

NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:[NSEntityDescription entityForName:entity inManagedObjectContext:self]];
[request setIncludesPropertyValues:NO];

NSArray *allObjects = [self executeFetchRequest:request error:error];

if (![self save:error])
    return NO;

for (NSManagedObject *object in allObjects)
    [self deleteObject:object];

return YES;
}

然后使用它只需：

- (void)deleteAllObjectsForEntityName:(NSString *) entity {

   NSError *error = nil;
   NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
   if (managedObjectContext != nil) {
       if (![managedObjectContext deleteAllObjectsForEntityName:entity withError:&error]) {
           NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
    }
 }
}

传递您的实体名称，它将全部删除： - ）

如何重置核心数据应用程序

1 个答案: