Question

I need to get the latest date from coredata

i found a way

NSSortDescriptor * sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"date" ascending:NO];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]];

[fetchRequest setFetchLimit:1];

so sort them by date and then pick the first

however can this not be done more optimal? this approach looks like a brute force

sort is nlogn, but simple search for the max is n

Answer 1

You can actually ask SQL for just that value, not the object with that value:

NSExpression *date = [NSExpression expressionForKeyPath:@"date"];
NSExpression *maxDate = [NSExpression expressionForFunction:@"max:"
    arguments:[NSArray arrayWithObject:maxDate]];
NSExpressionDescription *d = [[[NSExpressionDescription alloc] init] autorelease];
[d setName:@"maxDate"];
[d setExpression:maxSalaryExpression];
[d setExpressionResultType:NSDateAttributeType];

[request setPropertiesToFetch:[NSArray arrayWithObject:d]];

NSError *error = nil;
NSArray *objects = [managedObjectContext executeFetchRequest:request error:&error];
if (objects == nil) {
    // Handle the error.
} else {
    if (0 < [objects count]) {
        NSLog(@"Maximum date: %@", [[objects objectAtIndex:0] valueForKey:@"maxDate"]);
    }
}

This is described in more detail under Fetching Managed Objects -> Fetching Specific Values in the CoreData documentation.