An Important Distinction
There is a big difference between a value-based collection of pointers, and a pointer-based collection class. You can save yourself difficulty by understanding the distinction.
For example, declaring:
// value-based list of RWCString pointers
RWTValDlist< RWCString* > words;
gives you a value-based list, where the values are of type pointer to
RWCString. The collection class will concern itself only with the pointers, never worrying about the actual
RWCString objects they refer to. Now consider:
RWCString* ptr1 = new RWCString ("foo");
words.insert (ptr1);
RWCString* ptr2 = new RWCString ("bar");
std::cout << words.occurrencesOf (ptr2); // Prints 0
The above code prints 0 because the memory locations of the two string objects are different, and the collection class is comparing only the values of the pointers themselves (their addresses) when determining the number of occurrences.
Contrast that with the following:
// pointer-based list of RWCStrings
RWTPtrDlist<RWCString> words;
RWCString* ptr1 = new RWCString ("foo");
words.insert (ptr1);
// Different object, same string
RWCString* ptr2 = new RWCString ("foo");
std::cout << words.occurrencesOf (ptr2); // Prints 1
Here the collection class is parameterized by
RWCString, not
RWCString*, showing that only
RWCString objects, not pointers, are of interest to the list. But because it is a pointer-based collection class, communicating objects of interest is done via pointers to those objects. The collection class knows it must dereference these pointers, as well as those stored in the collection class, before comparing for equality.
