给CoreData添加新属性，就是给数据库加新字段，那么必须要进行数据库版本升级及CoreData数据迁移；
具体操作是
1.选择DemoCoreData.xcdatamodeld 文件，Editor ->Add Model Version ,输入新的版本名字；
2.在右侧的文件查看器窗口 的Model Version current 设置当前最新的版本名字；
3.在新数据模型的文件上添加字段，记得在类文件里也要添加上你添加的新字段，可以删除原来的类文件，重新生成manageobject类。
4.代码中加入 数据迁移的配置选项：
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
//
The persistent store coordinator for the application. This
implementation creates and returns a coordinator, having added the store
for the application to it.
//设置CoreData迁移配置
NSDictionary *options = [NSDictionarydictionaryWithObjectsAndKeys:@YES,NSInferMappingModelAutomaticallyOption, @YES,NSMigratePersistentStoresAutomaticallyOption, nil];
if (_persistentStoreCoordinator != nil) {
return_persistentStoreCoordinator;
}
// Create the coordinator and store
_persistentStoreCoordinator = [[NSPersistentStoreCoordinatoralloc] initWithManagedObjectModel:[selfmanagedObjectModel]];
NSURL *storeURL = [[selfapplicationDocumentsDirectory] URLByAppendingPathComponent:@"DemoCoreData.sqlite"];
NSError *error = nil;
NSString *failureReason = @"There was an error creating or loading the application's saved data.";
if (![_persistentStoreCoordinatoraddPersistentStoreWithType:NSSQLiteStoreTypeconfiguration:nilURL:storeURL options:options error:&error]) {
// Report any error we got.
NSMutableDictionary *dict = [NSMutableDictionarydictionary];
dict[NSLocalizedDescriptionKey] = @"Failed to initialize the application's saved data";
dict[NSLocalizedFailureReasonErrorKey] = failureReason;
dict[NSUnderlyingErrorKey] = error;
error = [NSErrorerrorWithDomain:@"YOUR_ERROR_DOMAIN"code:9999userInfo:dict];
// Replace this 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.
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return_persistentStoreCoordinator;
}
