More Exceptional C++

Chapter 27. (Im)pure Virtual Functions

Difficulty: 7

Does it ever make sense to make a function pure virtual, but still provide a body?

1. What is a pure virtual function? Give an example.

2. Why might you declare a pure virtual function and also write a definition (body)? Give as many possible reasons or situations as you can.

Solution

• 1. What is a pure virtual function? Give an example.

A pure virtual function is a virtual function you want to force concrete derived classes to override. If a class has any non-overridden pure virtuals, it is an “abstract” class, and you can't create objects of that type.

 // Example 27-1 // class AbstractClass { // declare ...