Question

I have a problem with core data when setting relationships:

The code below crashes randomly when setting the relationships between country and region.

If I disable the second for-loop, the method completes without errors.
Everything happens within the context living on the background-thread.

Again: I can create the objects for the regions and countries without trouble and they show up in the Simulators database just fine – but as soon as I try to set the relationships between then, the app crashes randomly.

Any thoughts ?

for (Region* region in regions) {        
    // only store if region code isn't empty
    if (region.m_RegionCode != nil && [region.m_RegionCode length] > 0) { 
        NSManagedObject* cdRegion = [NSEntityDescription insertNewObjectForEntityForName:CDREGION inManagedObjectContext:self.objectContextBackground];
        [cdRegion setValue:region.m_RegionCode forKey:@"code"];
        [cdRegion setValue:region.m_regioncodedescription forKey:@"name"];            
    }            
}
[self saveBackgroundContext];
 for (Region* region in regions) {        
    if (region.m_RegionCode != nil && [region.m_RegionCode length] > 0) { 
        NSManagedObject* cdRegion = [self getManagedObject:CDREGION withCode:region.m_RegionCode];
        NSManagedObject* CDCountry = [self getManagedObject:CDCOUNTRY withCode:region.m_countrycode];
        [cdRegion setValue:CDCountry forKey:@"country"];

    }            
}

Answer 1

well – just to let you know: it actually was the problem (I know – it is listed on top of all pages regarding this topic 🙂 that I used a context between threads.

I mixed up queues and threads. I created a single background-queue where I used my “background-context” … but of course i created several threads within that, who where interacting with the context… so…

btw: it was this excellent article that finally clarified it for me:
(came right in time 🙂
http://www.cimgf.com/2011/08/22/importing-and-displaying-large-data-sets-in-core-data/