UIAlertView does not show up from the Appdelegate - core-data

Question

I am working on core data migration. I am trying to handle exception when the persistent stores do not match and the app crashes. But before it crashes, i would like to let the user know (through an alert view) that he needs to uninstall the app first, and the re-install it. I have the code for the alert view in persistentStoreCoordinator accessor method, but the alertview never shows up.
Here is the code:
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
if (__persistentStoreCoordinator != nil) {
return __persistentStoreCoordinator;
}
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:#"ExchangeMail.sqlite"];
NSError *error = nil;
__persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
// Dictionary required to store the details of psc on the disk,
NSDictionary *sourceMetadata = [NSPersistentStoreCoordinator metadataForPersistentStoreOfType:NSSQLiteStoreType URL:storeURL error:&error];
// This BOOL value is required to check whether a migration is required or not.
BOOL pscCompatibile = [[self managedObjectModel] isConfiguration:nil compatibleWithStoreMetadata:sourceMetadata];
NSLog(#"Migration needed? %d", !pscCompatibile);
NSMutableDictionary *options = [[NSMutableDictionary alloc] init];
[options setValue:[NSNumber numberWithBool:YES] forKey:NSMigratePersistentStoresAutomaticallyOption];
[options setValue:[NSNumber numberWithBool:YES] forKey:NSInferMappingModelAutomaticallyOption];
UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:#"Non-matching Database File" message:#"The model configuration used to open the store is compatible with the one that was used to create the store. Please Uninstall the App and try again." delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil, nil];
[__persistentStoreCoordinator lock];
if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:options error:&error]) {
// dispatch_queue_t queue = NULL;
// queue = dispatch_get_main_queue();
// dispatch_async(queue, ^{
// [[NSFileManager defaultManager]removeItemAtURL:storeURL error:nil];
//
// [self.myAlertView show];
// });
[self.myAlertView show];
//exit(-1);
}
[__persistentStoreCoordinator unlock];
if(!pscCompatibile){
isMigrationRequired = YES;
}
return __persistentStoreCoordinator;
}