Memberwise Copying for Classes with Class Members

Suppose you use the String class, or, for that matter, the standard string class as a type for class members:

class Magazine
{
private:
    String title;
    string publisher;
...
};

String and string both use dynamic memory allocation. Does that mean you need to write a copy constructor and assignment operator for the Magazine class? No—at least not in itself. The default memberwise copying and assignment behavior does have some smarts. If you copy or assign one Magazine object to another, memberwise copying uses the copy constructors and assignment operators defined for the member types. That is, the String copy constructor will be used to copy the title member from one Magazine object to another, the String assignment operator will be used to assign the title member of one Magazine object to another, and so on. Things get more complicated, however, if the Magazine class needs a copy constructor and assignment operator for some other class member. In that case, those functions have to call the String and string copy constructors and assignment operators explicitly. But that’s a tale for Chapter 13, “Class Inheritance.”

Observations About Returning Objects

When a member function or standalone function returns an object, you have choices. The function could return a reference to an object, a constant reference to an object, an object, or a constant object. By now, you’ve seen examples of all but the last, so it’s a good time to review these options.