Delegate for ios app upgrade - objective-c

Question

Is there any delegate method that will be called when the user upgrades to or reinstalls a newer version of the iOS app?
I use Core Data to cache some information from server. When the schema of any entity is changed, I need to manually delete the SQLite database from the simulator, otherwise the app will crash on startup, with an error "The model used to open the store is incompatible with the one used to create the store." If there is any delegate method for app upgrade, the deletion could be automated.

Answer 1

You need to use CoreData versioning:
http://developer.apple.com/library/mac/#documentation/cocoa/conceptual/CoreDataVersioning/Articles/Introduction.html

Answer 2

Daniel Smith's answer is the proper one, but I just want to add how my app determines its been updated. I look keep a 'current version' string in the defaults. When the app starts up, I compare it to the current version:
defaults has no string - this is the first run of the app
defaults version is different - the user updated the app
defaults is the same - user just restarted the app
Sometimes its nice to know the above. Make sure to save the defaults immediately after you set the tag and do whatever versioning you want, so a crash doesn't have you do it again.
EDIT: how not to crash if he model changes. I use this now, keep the old repository, and tweaking the model, on every tweak it just removes the old one (if it cannot open it) and creates a new one. This is modeled on Apple's code but not sure about what changes I made. In any case you don't get a crash if the model changes.
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
//LTLog(#"_persistentStoreCoordinator = %#", _persistentStoreCoordinator);
if (_persistentStoreCoordinator)
{
return _persistentStoreCoordinator;
}
NSFileManager *manager = [NSFileManager defaultManager];
NSString *path = [[appDelegate applicationAppSupportDirectory] stringByAppendingPathComponent:[_dbName stringByAppendingPathExtension:#"SQLite"]];
storeURL = [NSURL fileURLWithPath:path];
BOOL fileExists = [manager fileExistsAtPath:path];
if(!fileExists) {
_didCreateNewRepository = YES;
}
if(_createNewRepository) {
[manager removeItemAtURL:storeURL error:nil];
if(fileExists) _didDestroyOldRepository = YES;
_didCreateNewRepository = YES;
}
while(YES) {
__autoreleasing NSError *error = nil;
_persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
if ([_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
break;
} else {
_persistentStoreCoordinator = nil;
[manager removeItemAtURL:storeURL error:&error];
if(fileExists) {
_didDestroyOldRepository = YES; // caller didn't want a new one but got a new one anyway (old one corrupt???)
_didCreateNewRepository = YES;
}
#ifndef NDEBUG
LTLog(#"CORE DATA failed to open store %#: error=%#", _dbName, error);
#endif
/*
Replace this implementation 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. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
Typical reasons for an error here include:
* The persistent store is not accessible
* The schema for the persistent store is incompatible with current managed object model
Check the error message to determine what the actual problem was.
*/
//LTLog(#"Unresolved error %#, %#", error, [error userInfo]);
//abort();
}
}
return _persistentStoreCoordinator;
}

Answer 3

Follow the blog its good:
http://blog.10to1.be/cocoa/2011/11/28/core-data-versioning/