Stephens' Visual Basic® Programming 24-Hour Trainer

Chapter 27. Fine-Tuning Classes

In Lesson 26 you learned how to build constructors, special methods that execute when an object is created. In this lesson you learn about other special methods you can give a class. In particular, you learn how to overload and override class methods.

OVERLOADING METHODS

Lesson 26 mentioned that you can give a class any number of constructors as long as they have different parameter lists. For example, it's common to give a class a parameterless constructor that takes no parameters, and one or more other constructors that take parameters.

Making multiple methods with the same name but different parameter lists is called overloading. Visual Basic uses the parameter list to determine which version to use when you invoke the method.

For example, suppose you're building a course assignment application and you have built Student, Course, and Instructor classes. You could give the Student class two versions of the Enroll method, one that takes as a parameter the name of the class in which the student should be enrolled and a second that takes a Course object as a parameter.

You could give the Instructor class similar versions of the Teach method to make the instructor teach a class by name or Course object.

Finally, you could give the Course class different Report methods that:

• Display a report in a dialog if there are no parameters

• Append a report to the end of a file if the method receives a FileStream as a parameter

• Save the report into a new file if the method ...