9.15. Wrap-Up

This chapter deepened our coverage of classes, using a Time class case study to introduce several new features. We used an include guard to prevent the code in a header (.h) file from being included multiple times in the same source code (.cpp) file. You learned how to use the arrow operator to access an object’s members via a pointer of the object’s class type. You learned that member functions have class scope—the member function’s name is known only to the class’s other members unless referred to by a client of the class via an object name, a reference to an object of the class, a pointer to an object of the class or the scope resolution operator. We also discussed access functions (commonly used to retrieve the values of data members or to test the truth or falsity of conditions) and utility functions (private member functions that support the operation of the class’s public member functions).

You learned that a constructor can specify default arguments that enable it to be called in a variety of ways. You also learned that any constructor that can be called with no arguments is a default constructor and that there can be at most one default constructor per class. We discussed destructors for performing termination housekeeping on an object of a class before that object is destroyed, and demonstrated the order in which an object’s constructors and destructors are called.

We demonstrated the problems that can occur when a member function returns a reference or a pointer to a private data member, which breaks the encapsulation of the class. We also showed that objects of the same type can be assigned to one another using default memberwise assignment—in Chapter 10, we’ll discuss how this can cause problems when an object contains pointer members.

You learned how to specify const objects and const member functions to prevent modifications to objects, thus enforcing the principle of least privilege. You also learned that, through composition, a class can have objects of other classes as members. We demonstrated how to use friend functions.

You learned that the this pointer is passed as an implicit argument to each of a class’s non-static member functions, allowing them to access the correct object’s data members and other non-static member functions. We used the this pointer explicitly to access the class’s members and to enable cascaded member-function calls. We motivated the notion of static data members and member functions and demonstrated how to declare and use them in your own classes.

In Chapter 10, we continue our study of classes and objects by showing how to enable C++’s operators to work with class-type objects—a process called operator overloading. For example, you’ll see how to overload the << operator so it can be used to output a complete array without explicitly using a repetition statement.