Automatic Lightwieight Migration for core data Problem - macos

Question

I'm having problem use Automatic Lightweight Migration Code in my App delegate !
I read all the apple's documentations about "Automatic Lightweight Migration" but after all I can't find my way to use the codes that is prepared to Automatic Lightweight Migration.
Recently, I just added some new Attribute to an Entity in my data model and I want to keep my old data.
my app delegate code is like this :
- (NSPersistentStoreCoordinator *) persistentStoreCoordinator {
if (__persistentStoreCoordinator) {
return __persistentStoreCoordinator;
}
NSManagedObjectModel *mom = [self managedObjectModel];
if (!mom) {
NSLog(#"%#:%# No model to generate a store from", [self class], NSStringFromSelector(_cmd));
return nil;
}
NSFileManager *fileManager = [NSFileManager defaultManager];
NSURL *applicationFilesDirectory = [self applicationFilesDirectory];
NSError *error = nil;
NSDictionary *properties = [applicationFilesDirectory resourceValuesForKeys:[NSArray arrayWithObject:NSURLIsDirectoryKey] error:&error];
if (!properties) {
BOOL ok = NO;
if ([error code] == NSFileReadNoSuchFileError) {
ok = [fileManager createDirectoryAtPath:[applicationFilesDirectory path] withIntermediateDirectories:YES attributes:nil error:&error];
}
if (!ok) {
[[NSApplication sharedApplication] presentError:error];
return nil;
}
}
else {
if ([[properties objectForKey:NSURLIsDirectoryKey] boolValue] != YES) {
// Customize and localize this error.
NSString *failureDescription = [NSString stringWithFormat:#"Expected a folder to store application data, found a file (%#).", [applicationFilesDirectory path]];
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
[dict setValue:failureDescription forKey:NSLocalizedDescriptionKey];
error = [NSError errorWithDomain:#"YOUR_ERROR_DOMAIN" code:101 userInfo:dict];
[[NSApplication sharedApplication] presentError:error];
return nil;
}
}
NSURL *url = [applicationFilesDirectory URLByAppendingPathComponent:#"FinancingPro.storedata"];
__persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:mom];
if (![__persistentStoreCoordinator addPersistentStoreWithType:NSXMLStoreType configuration:nil URL:url options:nil error:&error]) {
[[NSApplication sharedApplication] presentError:error];
[__persistentStoreCoordinator release], __persistentStoreCoordinator = nil;
return nil;
}
return __persistentStoreCoordinator;
Now I don't know how to change this code to have Automatic Lightweight Migration !
Please Note that my db is NOT SQLlite.

Answer 1

You need to set the options dictionary with the NSInferMappingModelAutomaticallyOption key here:
if (![__persistentStoreCoordinator addPersistentStoreWithType:NSXMLStoreType configuration:nil URL:url options:nil error:&error]) {
By passing a nil value for options you are telling the store to ignore any migration.