Question

I have a list of items in an entity in Core Data on the iphone all of them have an item_id integer attribute. I need to return the highest numbered item_id and the lowest numbered item_id that are in the table with one fetch request. I do not have any knowledge of what those numbers might be as they do not start at 0 and go up.

What would be the best way to accomplish this? Again, I know I can do it with 2 separate fetch requests, is there a way to do it with just one?

Answer 1

That’s a tricky one to do in only ONE fetch. I would do two fetches using the MAX and MIN functions / expressions. e.g.

NSExpression *minExpression = [NSExpression expressionForFunction:@”min:”
arguments:[NSArray arrayWithObject:keyPathExpression]];

If you absolutely have to do it in ONE fetch then I can only think to do a fetchAll and sort by the id, then get the first and last via:

[objects objectAtIndex:0]
[objects lastObject] 

Update 1:
Looks like this guy has a solution:
http://useyourloaf.com/blog/2012/1/19/core-data-queries-using-expressions.html