Common Programming Error 9.5

A compilation error occurs if a member object is not initialized with a member initializer and the member object’s class does not provide a default constructor (i.e., the member object’s class defines one or more constructors, but none is a default constructor).

Performance Tip 9.4

Initialize member objects explicitly through member initializers. This eliminates the overhead of “doubly initializing” member objects—once when the member object’s default constructor is called and again when set functions are called in the constructor body (or later) to initialize the member object.

Software Engineering Observation 9.11

If a data member is an object of another class, making that member object public does not violate the encapsulation and hiding of that member object’s private members. But, it does violate the encapsulation and hiding of the containing class’s implementation, so member objects of class types should still be private.