How can a base class protect derived classes so that changes to the base class will not affect them explain with example?

Answer 1

In order for a base class to protect derived classes, so that changes to the base class do not affect the derived classes, you must make sure that the public interface exposed by the base class does not change when the implementation of those public methods do change. You can also prevent inadvertant access to the base class attributes from the derived class, by making them private.

class base {

public:

base(...) {...}; /* constructor */

base~(...) {...}; /* destructor */

method(...) {...}; /* other public methods */

private:

... etc.

}

class child : base {

public:

...

private:

...

}

So long as the calling sequence and functionality (interface) of the base class public methods do not change, the implementation of those public methods can change, and the private methods and attributes can change, without impacting any child class.