添加新的核心数据模型版本后出错

Question

我添加了一个新的模型版本，并将核心数据模型设置为使用该新版本，但当应用程序尝试启动时出现此错误。

“用于打开持久存储的托管对象模型版本与用于创建持久存储的版本不兼容。”

我猜测问题在于当前的持久存储是模型的旧版本。有没有办法直接删除它，然后再创建一个新的？我不关心保存任何数据。

Answer 1

您必须在版本之间迁移。根据Apple的文档，如果更改很简单，则可以进行轻量级迁移。

http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/CoreDataVersioning/Articles/vmLightweight.html#//apple_ref/doc/uid/TP40008426-SW1

将这些选项添加到NSPersistentStoreCoordinator 似乎可以工作。

NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                                 [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
                                 [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];

    NSURL *url = [applicationFilesDirectory URLByAppendingPathComponent:@"YOURAPP.storedata"];
        persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:mom];
        if (![persistentStoreCoordinator addPersistentStoreWithType:NSXMLStoreType configuration:nil URL:url options:options error:&error]) {
            [[NSApplication sharedApplication] presentError:error];
            [persistentStoreCoordinator release], persistentStoreCoordinator = nil;
            return nil;
        }

    return persistentStoreCoordinator;

Answer 2

回答你的问题，“有没有办法删除它，这样它就可以创建一个新的？”

是的。

只需更改 App Delegate 中的 permanentStoreCoordinator getter 即可，如下所示：

- (NSPersistentStoreCoordinator *) persistentStoreCoordinator {
  if (persistentStoreCoordinator) return persistentStoreCoordinator;
  NSManagedObjectModel *mom = [self managedObjectModel];
  if (!mom) {
    NSAssert(NO, @"Managed object model is nil");
    NSLog(@"%@:%s No model to generate a store from", [self class], (char *)_cmd);
    return nil;
  }
  NSFileManager *fileManager = [NSFileManager defaultManager];
  NSString *applicationSupportDirectory = [self applicationSupportDirectory];
  NSError *error = nil;
  if ( ![fileManager fileExistsAtPath:applicationSupportDirectory isDirectory:NULL] ) {
    if (![fileManager createDirectoryAtPath:applicationSupportDirectory withIntermediateDirectories:NO attributes:nil error:&error]) {
      NSAssert(NO, ([NSString stringWithFormat:@"Failed to create App Support directory %@ : %@", applicationSupportDirectory,error]));
      NSLog(@"Error creating application support directory at %@ : %@",applicationSupportDirectory,error);
      return nil;
    }
  }
  NSURL *url = [NSURL fileURLWithPath: [applicationSupportDirectory stringByAppendingPathComponent: @"storedata"]];
  persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel: mom];
  if (![persistentStoreCoordinator addPersistentStoreWithType:NSXMLStoreType 
                                                configuration:nil 
                                                          URL:url 
                                                      options:nil 
                                                        error:&error]){
    // EDIT: if error opening persistent store, remove it and create a new one
    if([[error domain] isEqualToString:@"NSCocoaErrorDomain"] && [error code] == 134100) {
      NSLog(@"Core Data model was updated.  Deleting old persistent store.");
      [[NSFileManager defaultManager] removeItemAtURL:url error:nil];
      if (![persistentStoreCoordinator addPersistentStoreWithType:NSXMLStoreType 
                                                configuration:nil 
                                                          URL:url 
                                                      options:nil 
                                                        error:&error]){
        [[NSApplication sharedApplication] presentError:error];
        [persistentStoreCoordinator release], persistentStoreCoordinator = nil;
        return nil;
      }
    } else {
        [[NSApplication sharedApplication] presentError:error];
        [persistentStoreCoordinator release], persistentStoreCoordinator = nil;
        return nil;
    }
    //
  }    
  return persistentStoreCoordinator;
}

Answer 3

找出您的应用程序存储文档的位置并将其放入垃圾箱。

但作为扩展评论，您可能希望检查 NSPersistentStoreCoordinator 中的显式和隐式迁移以及中的选项的可能性。

- (NSPersistentStore *)addPersistentStoreWithType:(NSString *)storeType 配置：(NSString *)configuration URL:( NSURL *)storeURL options:(NSDictionary *)options error:(NSError **)error

根据版本的不同，您可以通过传递 NSMigratePersistentStoresAutomaticallyOption & 来让它自动发生。 NSInferMappingModelAutomaticallyOption

还有

- (NSPersistentStore *)migratePersistentStore:(NSPersistentStore *)store toURL:(NSURL *)URL 选项:(NSDictionary *)options withType:(NSString *)storeType error:(NSError **）错误