Computer Programming Concepts and Visual Basic David I. Schneider

358 Computer Programming Concepts and Visual Basic
10. In the same manner as in Steps 7–9, create the following pair of property procedures
that will be used to retrieve and assign values to the variable m_ssn.
Public Property Get SocSecNum() As String
SocSecNum = m_ssn
End Property
Public Property Let SocSecNum(ByVal vNum As String)
m_ssn = vNum
End Property
11. Property procedures can be typed directly into the class module without the use
of Add Procedure. Also, property procedures needn’t come in pairs. For
instance, if we wanted the value of a member variable to be “write only,” we
would use a Property Let procedure and have no Property Get procedure. Type
the following two property procedures into the class module. The inclusion of
the word Public is optional.
Property Let midGrade(ByVal vGrade As Single)
m_midterm = vGrade
End Property
Property Let finGrade(ByVal vGrade As Single)
m_final = vGrade
End Property
12. Create the following ordinary Public function with the name SemGrade.
Public Function SemGrade() As String
Dim grade As Single
grade = (m_midterm + m_final) / 2
grade = Round(grade) ‘Round the grade
Select Case grade
Case Is = 90
SemGrade = “A”
Case Is = 80
SemGrade = “B”
Case Is = 70
SemGrade = “C”
Case Is = 60
SemGrade = “D”
Case Else
SemGrade = “F”
End Select
End Function
(This function will be used by our program to invoke a method requesting an
object to calculate a student’s semester grade.)
13. From the File menu, click on Save CStudent As and save the class module with
the name 13-1-1S.cls. (We chose this name since the class will be used in
Example 1. Another good choice of name would have been Student.cls. The
extension cls is normally given to files holding class modules.)
14. Click on the form window to activate it. We can now write a program that creates
an object, call it pupil, that is an instance of the class and uses the object
to calculate a student’s semester grade. The object variable is declared (in the
general declarations section of the code module) with the statement
Private pupil As CStudent