CoreData - One method to conquer them all! Create fetch reeuests from string predicates.

gistfile1.m

/**
 * Return an array with objects found in the local database for the given predicate.
 */
-(NSArray *)fetchEntity:(NSString *)entityName withPredicateFormat:(NSString *)format, ... {
    
    NSManagedObjectContext *managedObjectContext = [RKObjectManager sharedManager].objectStore.managedObjectContext;
    
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
	NSEntityDescription *entity = [NSEntityDescription entityForName:entityName 
                                              inManagedObjectContext:managedObjectContext];
	[request setEntity:entity];
    
	va_list args;
	va_start(args, format);
	NSPredicate *predicate = [NSPredicate predicateWithFormat:format arguments:args];
	va_end(args); 
	[request setPredicate:predicate];
    
	
	NSError *error = nil;
	NSArray *array = [managedObjectContext executeFetchRequest:request error:&error];
	if (error != nil) {
		NSLog(@"ERROR FETCHING DATA FROM DB FOR PREDICATE");
	}
	
    [request release];
	
	return array;
}




- (void)fetchObjects {
	NSArray *array = [self fetchEntity:@"Vehicle" withPredicateFormat:@"latitude > %f AND latitude < %f AND longitude > %f AND longitude < %f",
                      latitudeStart, latitudeStop, longitudeStart, longitudeStop];

}

To query my sqlite database in Mac OS and iOS I am using lots of predicates and I hate to repeat myself. This method makes things easier in most cases.