Chapter 11, Problem 1E

Explanation of Solution

Given: The network project version and the display method is in the Post class.

To find:

The display method is shifted into the class MessagePost and PhotoPost.

The result on compilation of the program.

Solution:

The program shows compile time error after shifting the display() method from Post class to MessagePost and PhotoPost.

The MessagePost and PhotoPost are the subclasses of Post class. The private members can access only from the member function of the same class. The display() method tries to access the private members of the Post class from the subclasses MessagePost and PhotoPost. Therefore, it shows compile time error. A public member function created in the Post class and calling that from the display method removes error.

It also shows error in NewsFeed class because the NewsFeed class calls the display() method with the object of type Post and the display method is not in the Post class. Hence, it shows compile time error.