Coredata provides a lightweight auto data migration method for the following conditions:
1. Simply add a new column.
2. Change a column to optional.
3. Change a optional column to compulsory, but have default value.
Step 1:
Create a new data version
1. Editor -> Add Model Version (expand your xcdatamodeld item) , type a name
2. Client on the xxxx.xcdatamodeld file and in the attribute page, set the current version
Step 2:
1. In App delegate , in method "persistentStoreCoordinator" change as follow:
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {if (__persistentStoreCoordinator != nil) {return __persistentStoreCoordinator;}NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"WorkXP.sqlite"];NSError *error = nil;__persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];// handle db upgradeNSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,[NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error]) {// Handle error} return __persistentStoreCoordinator;}
After that, for a lightweight data migration, user don't need to remove the old version app before they install the new one.
