Learning to Program in C++

Review

We started this chapter with the DatedStockItem class from Chapter 9, which extended the StockItem class by adding an expiration date field to the member variables that DatedStockItem inherited from the StockItem class. While this was a fine solution to the problem of creating a class based on the StockItem class without having to rewrite all the functioning code in the latter class, it didn't solve the bigger problem: how to create a vector of objects that might or might not have expiration dates. That is, we wanted to be able to mix StockItem objects with DatedStockItem objects in the same vector, which can't be done directly in C++.

Part of this difficulty was solved easily enough by making a vector of StockItem*s (i.e., pointers to ...