Re: [Swarm-Support] How to prevent sending a message to a dropped object?

[Paul Johnson]

martijn cox wrote:
> Well, that would indeed work, but the thing is: I don't have the pointer to
> the object available. All I can do is loop over a List of agents like so:
>
>  while( (agent = [index next]) != nil )
>     {
>       if ([agent getBirthAction])
>        [lifeMutationSchedule remove: [agent getBirthAction]];
>       [_agentList remove: agent];
>       [agent drop];
>       agent = nil; // ***
>     }

remove returns a pointer to the removed object. But I don't think you 
should remove items this way.

FIrst, don't use the while construct, use for.  If your while finds a 
nil in your list, the iterating will stop prematurely. Second, you are 
wrecking  the index by removing a member while iterating.  That's bad.

I can give you a much better algorithm for doiing this that fixes all of 
these problems.  Then it will be much cleaner & faster to remove with 
the index.

id agent, index;

index = [agentList begin: [self getZone]];

for(agent = [index next]; [index getLoc]==Member; agent = [index next])
{

   if ([agent getBirthAction])
        {
           id theAgent; 
           [lifeMutationSchedule remove: [agent getBirthAction]];
           theAgent = [index remove];
           [theAgent drop];
           theAgent = nil;
         }
}

Actions on indexes to remove items are
1. safe to the index and
2. Much Much faster than searching through a collection to find 
something and remove it.



--
Paul E. Johnson                       email: address@hidden
Dept. of Political Science            http://lark.cc.ku.edu/~pauljohn
1541 Lilac Lane, Rm 504
University of Kansas                  Office: (785) 864-9086
Lawrence, Kansas 66044-3177           FAX: (785) 864-5700