Where to Put Code Configuring Persistent Store for Migration - objective-c

Question

I have a Mac App already created and distributed on the App Store to many customers, and I need to add an attribute to the Core Data Model. I read the documentation provided by Apple, available here.
However, it gives this block of code to enable automatic migration:
NSError *error;
NSPersistentStoreCoordinator *psc = <#The coordinator#>;
NSURL *storeURL = <#The URL of a persistent store#>;
NSDictionary *optionsDictionary =
[NSDictionary dictionaryWithObject:[NSNumber numberWithBool:YES]
forKey:NSMigratePersistentStoresAutomaticallyOption];
NSPersistentStore *store = [psc addPersistentStoreWithType:<#Store type#>
configuration:<#Configuration or nil#>
URL:storeURL
options:optionsDictionary
error:&error];
.. And I have no idea where to put that. Someone mentioned (in another thread) that it goes into a PersistentStoreCoordinator, however, I simply used the default Cocoa App Template with "Use Core Data for Storage" enabled. I had to create my own AppDelegate and never saw anything about a PersistentStoreCoordinator (and still don't. I've tried creating a new app just to check). Any help here? I'm new to Cocoa but my app works perfectly fine without a PersistentStoreCoordinator, which is why I haven't implemented one yet.. I do have an AppDelegate I created, but when I put this code in there it throws many errors. HELP :/
EDIT (for nick): Here is the new code:
And my header file:

Answer 1

Here you go: Core Data relevant header and methods.
Application Delegate Header - Core Data relevant parts
#interface CoreDataFirstStepsAppDelegate : NSObject <UIApplicationDelegate>
{
// ...
#private
NSManagedObjectContext *managedObjectContext_;
NSManagedObjectModel *managedObjectModel_;
NSPersistentStoreCoordinator *persistentStoreCoordinator_;
}
// ...
#property (nonatomic, retain, readonly) NSManagedObjectContext *managedObjectContext;
#property (nonatomic, retain, readonly) NSManagedObjectModel *managedObjectModel;
#property (nonatomic, retain, readonly) NSPersistentStoreCoordinator *persistentStoreCoordinator;
Application Delegate Implementation - Core Data relevant parts
/**
Returns the managed object context for the application.
If the context doesn't already exist, it is created and bound to the persistent store coordinator for the application.
*/
- (NSManagedObjectContext *)managedObjectContext {
if (managedObjectContext_ != nil) {
return managedObjectContext_;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil) {
managedObjectContext_ = [[NSManagedObjectContext alloc] init];
[managedObjectContext_ setPersistentStoreCoordinator:coordinator];
}
return managedObjectContext_;
}
/**
Returns the managed object model for the application.
If the model doesn't already exist, it is created from the application's model.
*/
- (NSManagedObjectModel *)managedObjectModel {
if (managedObjectModel_ != nil) {
return managedObjectModel_;
}
NSString *modelPath = [[NSBundle mainBundle] pathForResource:#"CoreDataFirstSteps" ofType:#"momd"];
NSURL *modelURL = [NSURL fileURLWithPath:modelPath];
managedObjectModel_ = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
return managedObjectModel_;
}
/**
Returns the persistent store coordinator for the application.
If the coordinator doesn't already exist, it is created and the application's store added to it.
*/
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
if (persistentStoreCoordinator_ != nil) {
return persistentStoreCoordinator_;
}
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:#"CoreDataFirstSteps.sqlite"];
NSError *error = nil;
persistentStoreCoordinator_ = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
if (![persistentStoreCoordinator_ addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
NSError *error;
NSURL *storeURL = storeURL;
NSPersistentStoreCoordinator *psc = persistentStoreCoordinator_;
NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption,
[NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];
if (![psc addPersistentStoreWithType:NSSQLiteStoreType
configuration:nil
URL:storeURL
options:options
error:&error])
{
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
}
return persistentStoreCoordinator_;
}
/**
Returns the URL to the application's Documents directory.
*/
- (NSURL *)applicationDocumentsDirectory {
return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}