Is NSDictionary Defined?

Question

I have a NSDictionary that might be getting set inside a loop. At the end of the loop I want to find out if the dictionary has been defined. Here is an example:

NSDictionary *myDict;

for (int i=0; i < 100; i++){
    if (thisCondition){
        myDict = [NSDictionary dictionaryWithObjectsAndKeys:etc, nil];
    }
}

if (myDict) {
     [self doSomething];
}

Unfortunately, the test of myDict passes every time, whether myDict has been alloc'ed or not. Trying to pass any methods to myDict, like [myDict count], give a exc_bad_access because it has not been alloc'ed. So it is kind of a no man's land.

Is there a way to accomplish this? I realize I could switch to a NSMutableDictionary, define it, add to it in the loop, and test for a count, but that is not my preference.