make two different fetch request per one method - looks like impossible - cocoa

Question

Dear community.
I was find a trouble for using a core data. Here is description:
From my AppDelegate i called my own class:
InitUpdateIXC *initAndUpdate = [[[InitUpdateIXC alloc] init] autorelease];
[initAndUpdate updateCarrierList:self.managedObjectContext];
Then i using there couple of methods, which update managedObjectContext, insert, add some entities e.t.c.
In this case i find limitation to using predicate twice per method:
First using working fine, and i seen results inside request:
NSFetchRequest *requestDestinationsForSale = [[NSFetchRequest alloc] init];
[requestDestinationsForSale setEntity:[NSEntityDescription entityForName:#"DestinationsListForSale"
inManagedObjectContext:managedObjectContext]];
[requestDestinationsForSale setPredicate:[NSPredicate predicateWithFormat:#"carrier.name like %#",carrierName]];
NSArray *destinationsForSale = [managedObjectContext executeFetchRequest:requestDestinationsForSale error:&error];
Inside the loop around MO:
for (NSManagedObject *destinationForSale in destinationsForSale)
{
for (NSManagedObject *code in [destinationForSale valueForKey:#"codesvsDestinationsList"])
{
i try to make new fetchRequest:
NSFetchRequest *requestDestinationWeBuy = [[[NSFetchRequest alloc] init] autorelease];
[requestDestinationWeBuy setEntity:[NSEntityDescription entityForName:#"DestinationsListWeBuy"
inManagedObjectContext:managedObjectContext]];
NSError *error = nil;
[requestDestinationWeBuy setPredicate:[NSPredicate predicateWithFormat:#"carrier.name like %#",carrierName]];
NSArray *destinationWeBuyList = [managedObjectContext executeFetchRequest:requestDestinationWeBuy error:&error];
ops... NSArray is empty...
if i do a same when i call method from AppDelegate:
[initAndUpdate updateRoutingTable:self.managedObjectContext];
It's a same class, same method, just called from main AppDelegate and little bit changed for using a just managed context, everything working fine.
Looks like managedObjectContext have final updates only when we leave class methods, which make updates.
Any comment will appreciated.

Answer 1

In your first fetch you are fetching on the entity DestinationsListForSale but in the second you are fetching on the entity DestinationsListWeBuy. The simplest explanation is that the same predicate does not produce the same result when applied to different entities.
Depending on the specifics of both the entities and the data being persistent at any one time, the same predicate will produce different outcomes when applied against different entities.
Indeed, that would be the expected behavior.