core data :fetching data from entity

Question

i have to use following query for fetching data:

SELECT * FROM t1.guides AS t1 JOIN guide_category_int AS t2 ON t1.id = t2.guide_id WHERE t2.category_id = 'category_id' AND t1.start_date >= 'today()' AND t1.end_date <= 'today()' ORDER BY t1.name ASC

How can I use this in core data?

Answer 1

Your fetch request will be something like this:

NSManagedObjectContext *context = ...
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Guides" inManagedObjectContext:context];
[fetchRequest setEntity:entity];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"guide.category_id == %@ and start_date >= %@ and end_date <= %@", @"category_id", [NSDate date], [NSDate date]]];
[fetchRequest setPredicate:predicate];
NSSortDescriptor *sort = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]];
[sort release];
NSError *error;
NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&error];
if ([fetchedObjects count] > 0) {
    //...
}
[fetchRequest release];

Also you can enable SQLDebug to see raw sql requests, and play with predicate and sort descriptor as you want. How to enable described there