Re: Ordered Core Data

FROM : Bill Bumgarner
DATE : Wed Jun 15 01:44:13 2005

On Jun 14, 2005, at 4:27 PM, John Brownlow wrote:
> Or you can start writing linked lists which do much the same thing 
> except that they maintain pointers to 'nextItem' instead of keeping 
> an index, but it's just as ugly.


Actually, depending on context of implementation, using a linked list 
is both quite easy and very efficient.  Obviously, inserting/deleting 
objects into a linked list is trivial and fast if you have both a 
next and a previous pointer.  Given that Core Data will maintain the 
inverse relationship automatically, it will also maintain the linked 
list pointers automatically.

Given that many UI type usage contexts will require all of the 
objects to be faulted into memory anyway, walking the "next" 
relations and filling an NSMutableArray for display purposes is about 
three lines of code.

So, for the particular example of Screenplay -> Scenes, a linked list 
might very well be a totally acceptable way of modeling this.

In this particular example, the amount of overhead in the form of 
additional lines of code incurred by the developer is pretty trivial.

Yeah -- it is a bummer that Core Data doesn't have direct modeling of 
ordered relationships.  See my other email for why that decision was 
made.

b.bum