Question

I have a very strange error using NSMutableArray in cocos2d/xcode

In my code, I have a NSMutableArray containing object A

NSMutableArray *peasantArray;

and another NSMutableArray contain object B

NSMutableArray *treeArray;

in the scheduled update function, I called another function which is essentially the following functionality:
I would loop through all the object A inside the *peasantArray, and if any peasant object has a variable var == GameEntityCommandIdling, I would modify the object B in the second NSMutableArray *treeArray,

The issue is that I notice sometimes after I modified the object A inside the peasantArray, the modified variable (var) is being modified/updated inside the object A after by printing out the variable status in a scheduled fashion; but if I am to loop through the NSMutableArray *peasantArray again in the next schedule (1/30s), I will again find the object A with the older/un-updated variable (var), and this is causing my algorithm to be wrong,

However, if I loop through the NSMutableArray *peasantArray less than 1second, each time I would see the variable (var) for object A correctly as the updated variable value,

So is there a limit on how fast I can iterate over the NSMutableArray?

here are some piece of code that I basically just mentioned,

NSMutableArray *peasantArray;
NSMutableArray *treeArray;

…..

peasantArray = [[[NSMutableArray alloc] initWithCapacity:1]retain];
for(int i = 0; i < 1; i++)
{
    Peasant *A = [[Peasant alloc] init];
    [peasantArray addObject:A];
}

….
//inside the update()

for (int i = 0;i < [peasantArray count];i++)
{
    Peasant *A = [peasantArray objectAtIndex:i];
    if (A.status == something)
    {
         printf("A.status is something\n");
         A.status = sometingelse;

        ...
         //update other things not related to this NSMutableArray or object
    }
}

…..

SO the error is that sometimes I will have multiple printf of “A.status is something”, although only one of it should be printed,

I really appreciate any help,

Thanks,

Answer 1

So is there a limit on how fast I can iterate over the NSMutableArray?

Definitely no. That would be the stupidest implementation of an array I’d ever encountered. 🙂

The simplest explanation is usually the answer. You say the message is printed more than once. Well have you checked that maybe more than one Peasant has its status set to something?

If that’s not the case, are you certain the status update is printed twice in the same frame, and not twice in two subsequent updates?

Earlier on you seemed to indicate that the effect of iterating over one array and modifying the other array’s objects is invalidated somehow. That made me want to point out that if you have the same object in both arrays, modifying the object’s properties in array A will also modify the properties of the same object contained in array B.

You may want to give breakpoints a(nother) try. The problem should be easy to locate when you step through the code.