Lab 7 Polymorphism and Exceptions




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Lab 7

Polymorphism and Exceptions
For this lab we will continue working with the shapes developed for Lab 6.
(7 pts) Implementing Polymorphism
Use the classes from Lab 6 (Shape, Rectangle, Circle, and Square) to create polymorphism. Answer the
questions below and implement the polymorphism in the appropriate location of the interface and
implementation files.
Which function(s) are you going to make polymorphic?
How will you make it polymorphic?
Can it be a pure virtual function?
Which class have you made an abstract base class?
(5 pts) Testing Polymorphism
Modify your application.cpp file to show polymorphism by making a function that prints the information
of a shape. In this function, you will print the name, color, and area of the shape. You should pass your
shape by reference (or address explicitly) to have polymorphism.
void print_shape_info(Shape &);
(3 pts) Exceptions
After you’ve convinced yourself and the TAs that you have successfully implemented polymorphism for
your shapes, it is time to add some error handling. Since constructors don’t return anything, throwing an
exception during object construction is one of the best ways to signal an error with the construction.
Throw an exception in your constructors if the user does not provide a valid argument for their member
variables. The constructors should throw an invalid_argument exception, when the user tries to create
an object that would result in an area of zero. You’ll need to add the statement below to your function
throw invalid_argument(“Invalid constructor argument”);
First, run your program with trying to pass an invalid argument to your constructor to see what it does
now that your function throws an exception, and you are not catching it.

Now, catch the exception so that it doesn’t have an error! Remember, you can use the what() member
function to see your message from the invalid argument exception.