On Jul 27, 2008, at 12:33 AM, Mark Teagarden wrote:
Hi,
I'm working on a strategy game in which a NSMutableArray called
'army' contains a series of Unit objects. Each Unit contains a
property called next_unit, which is a pointer to the next unit in
the array - I'm implementing a linked-list so that units can be
moved sequentially.
Army starts off with six units, which are assigned one at a time to
the array:
for(i=0;i<6;i++){
u = [[Unit alloc] initWithPositionX:24+i Y:14-i];
[army addObject:u];
...
[u release];
}
Obviously when the first unit is added, there's nothing for
next_unit to point to, so I have to go back and do it on the next
loop iteration, which is where my problem arises:
if(i > 0) [army objectAtIndex:i-1].next_unit = [army lastObject];
Clearly, what I want to do is get the next-to-last unit in army and
point its next_unit pointer to the most recently added unit.
However, XCode she don't-a like this:
error: request for member 'next_unit' in something not a structure
or union
Is there a recommended way for accessing an ivar with synthesized
gettors/settors, that belongs to a returned object?
I hope I've explained my problem clearly enough. Thanks for an
advice you may offer.
Mark
You will need to cast the object returned from the array to your Unit
class:
if(i > 0) (Unit*)[army objectAtIndex:i-1].next_unit = [army
lastObject];
As a suggestion, if the order that Units move in is different than the
index in the army array you could just create a second array (say
'marchingOrder') that has the same Unit objects in it ordered as you
want them. Items in an NSMutableArray can be inserted and removed from
any index and can be reordered however you want.
--Nathan
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