Re: Implementing NSFastEnumeration

On Oct 1, 2009, at 11:30 AM, Christiaan Hofman wrote:
>
[..]

> While this works for small arrays, for larger arrays this gives a  
> memory access crasher. The reason seems to be that NSArray can  
> return more items than len (the size of stackbuf) in a single call.
>
Correct. The trick is to use a variable in the state to note you  
count. state->state happens to be 0 when first called, and OS X will  
not touch it. So you can use it to remember where you were at for the  
next call. See my example code.

> And another question I have been unable to find an answer to in the  
> docs. Foundation collections are implemented as class clusters. So  
> is NSFastEnumeration implemented as a primitive or a derived method?  
> In other words: when I subclass NSArray (or another collection  
> class), does it already have a default implementation of  
> NSFastEnumeration, or am I forced to always implement it when I want  
> to use for(...in...)?
>
AFAIK subclassing class clusters doesn't work, which is why I think  
they are a poor design.

Gerd