CoreData 添加新字段

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;

}