Computer Programming Concepts and Visual Basic David I. Schneider

Task Statement
Assign a value to a property objectName.propertyName = value
Display the value of a property picBox.Print objectName.propertyName
Carry out a method objectName.methodName(arg1, ...)
Raise an event RaiseEvent eventName
The following walkthrough creates a student class and a program that uses that class.
The data stored by an object of this class are name, social security number, and grades on
two exams (midterm and final).
1. Start a new program.
2. From the Project menu on the toolbar, click on Add Class Module.
3. Double-click on Class Module in the Add Class Module dialog box. (The window
that appears looks like an ordinary code window.)
4. If the Properties window is not visible, press F4 to display it. (Notice that the
class has the default name Class1.)
5. Change the setting of the Name property to CStudent. (We will follow the common
convention of beginning each class name with the uppercase letter C.)
6. Type the following lines into the code module.
Private m_name As String
Private m_ssn As String
Private m_midterm As Single
Private m_final As Single
(These lines of code declare four variables that will be used to hold data. The
word Private guarantees that the variables cannot be accessed directly from outside
the object. In object-oriented programming terminology, these variables
are called member variables (or instance variables). We will follow the common
convention of beginning the name of each member variable with the prefix
“m_”.)
7. From the Tools menu on the toolbar, click on Add Procedure. (As before, an
Add Procedure dialog box will appear.)
8. Type “Name” into the Name text box, click on Property in the Type frame, and
click on OK. The following lines will appear in the class module window.
Public Property Get Name() As Variant
End Property
Public Property Let Name(ByVal vNewValue As Variant)
End Property
9. Change the words Variant to String, the word vNewValue to vName, and type
code into the two property procedures as shown below.
Public Property Get Name() As String
Name = m_name
End Property
Public Property Let Name(ByVal vName As String)
m_name = vName
End Property
The first procedure will be called by our program to retrieve the value of the
variable m_name and the second procedure will be called to assign a value to
the variable m_name.
Classes and Objects 357