When is NSEnumerator finished?

How do we know when enumeration is finished? The docs say: the return value of

nextObject

is nil when all objects have been enumerated. I was hoping to implement some "delegate-like" behavior whereby ...

if (nextObject == nil) { 
    do something because we're done!
}

But I see there is no such thing as:

enumerationDidFinish:

where in the following block could I check for the enumerator to be complete?

NSArray *anArray = // ... ;
NSEnumerator *enumerator = [anArray objectEnumerator];
id object;

while ((object = [enumerator nextObject])) {
    // do something with object...
}

When the while loop finishes, you know the enumeration is complete. You could call the delegate method then.