Looking Ahead to Composition and Inheritance
Often, classes do not have to be created “from scratch.” Rather, they can include objects of other classes as members or they may be derived from other classes that provide attributes and behaviors the new classes can use. Such software reuse can greatly enhance productivity and simplify code maintenance. Including class objects as members of other classes is called composition (or aggregation) and is discussed in Section 9.11. Deriving new classes from existing classes is called inheritance and is discussed in Chapter 11.