This chapter includes:

Inheritance of is-a relationship

How to publicly derive one class from another

Protect access

Constructor member initialization list

Force up and down

Virtual member function

Early (static) and late (dynamic) binding

Abstract base class

Abstract base class

Pure virtual function

When and how to use public inheritance

Foreword:

Many vendors provide class libraries, which consist of class declarations and implementations, which combine data representation and class methods to provide a more complete package than function libraries.For example, a single class can provide all the resources for managing dialog boxes.Usually class libraries are provided as source code, which means that they can be modified to suit your needs.
C++ provides a better way to extend and modify classes than modify the source code, namely class inheritance.It can derive a new class from an existing class, and the derived class inherits the features and methods of the original class (base class).
The following are some of the work that can be accomplished through inheritance:
1. Functions can be added on the basis of existing classes.For example, the array class can add mathematical operations.
2, can add data to the class.For example, a string class can derive a class and add a data member that specifies the color of the string. 3. The behavior of the class method can be modified.For example, for a Passenger class that represents a service provided to airline passengers, a VipClassPassenger class that provides higher-level services can be derived.
The inheritance mechanism only needs to provide new features, and the class can be derived without accessing the source code.Therefore, for header files and compiled code that only provide class methods, new classes can still be derived from classes in the library.And you can distribute your class to others without exposing the implementation, while also allowing others to add new features to the class.