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如何删除Xcode中的旧数据模型？菜单上禁用该选项.(我想删除的模型尚未向公众发布 - 它们是临时开发模型.)

重命名.xcdatamodel文件需要做什么.重命名.xcdatamodel文件名,以及更改...

NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"newfilename" withExtension:@"momd"];
__managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];    
return __managedObjectModel;

和

NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"newfilename.sqlite"];

不起作用!我收到以下错误:

2011-04-11 17:19:54.164 ProjectName[5826:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Cannot create an NSPersistentStoreCoordinator with a nil model'
*** Call stack at first throw:
(
    0   CoreFoundation                      0x00fa15a9 __exceptionPreprocess + 185
    1   libobjc.A.dylib                     0x010f5313 objc_exception_throw + 44
    2   CoreData                            0x00013853 -[NSPersistentStoreCoordinator initWithManagedObjectModel:] + 419
    3   ProjectName                         0x00003471 -[ProjectNameAppDelegate persistentStoreCoordinator] + 257
    4   ProjectName                         0x000031a4 -[ProjectNameAppDelegate …