iOS - How can I sort the managed objects fetched from CoreData? - iphone

Question

This is how i am inserting the data,
NSEntityDescription * entityDescription = [NSEntityDescription entityForName:[DOSnow entityDescription] inManagedObjectContext: proxy.managedObjectContext];
DOCurrentCondition *doSnow = [[[DOSnow alloc] initWithEntity:entityDescription insertIntoManagedObjectContext: proxy.managedObjectContext] autorelease];
NSXMLElement *snowConditionsElement = [[roseElement elementsForName:SNOW] lastObject];
NSArray *snowElements = [snowConditionsElement children];
for (NSXMLElement *snowElement in snowElements)
{
NSEntityDescription * entityDescription = [NSEntityDescription entityForName:[DOPair entityDescription] inManagedObjectContext: proxy.managedObjectContext];
DOPair *pair = [[[DOPair alloc] initWithEntity:entityDescription insertIntoManagedObjectContext: proxy.managedObjectContext] autorelease];
pair.key = [snowElement name];
pair.value = [snowElement stringValue];
[doSnow addConditionsObject: pair];
}
[proxy save];
And this is how i am fetching the data,
- (NSArray *) fetchSnowConditions
{
ApplicationFacade *appFacade = [ApplicationFacade appFacade];
NSManagedObjectContext *context = appFacade.rProxy.managedObjectContext;
NSFetchRequest * request = [[[NSFetchRequest alloc] init] autorelease];
[request setEntity:[NSEntityDescription entityForName:[DOSnow entityDescription] inManagedObjectContext:context]];
NSError *error;
NSArray *result = [context executeFetchRequest:request error:&error];
return result;
}
So i am not getting the data in same order as i inserted.

Answer 1

You have to use [NSFetchRequest setSortDescriptor:] to get a meaningful ordering of your results. The NSFetchRequest documentation doesn't say anything about the default order of the results, so it's not a good idea to assume there is any.
Of course, in order to correctly specify the sort descriptor, you probably need to add a field to your managed objects to sort on, and assign a value to it when creating the objects. It could be an incrementing index field, a creation date, or something like that.