How To Use the CallByName Function to Run a Procedure (186143)

SUMMARY

The CallByName function provides Visual Basic 6.0 with the ability to call a property or method of an object using a string at run-time. Unlike the previous versions of Visual Basic in which methods and properties had to be known at design-time, the CallByName function allows for a great deal of flexibility at run-time. The use of this function is limited to OLE servers and Visual Basic class modules.

MORE INFORMATION

The following sample demonstrates how to use the CallByName function to call a method, a Property Let, and a Property Get. For more information on the CallByName function, please refer to the Visual Basic Help Files and the Books On-Line.

Steps to Create Sample Project

Start a new Standard EXE project in Visual Basic. Form1 is created by default.
Add a Class Module (Class1) to the project.

Add the following code to the Class Module:

      Option Explicit
      Private MyPropValue As Integer

      Public Function Multiply(x As Integer, y As Integer) As Integer
         Multiply = x * y
      End Function

      Public Property Get MyProperty() As Variant
         MyProperty = MyPropValue
      End Property

      Public Property Let MyProperty(ByVal vNewValue As Variant)
         MyPropValue = vNewValue
      End Property

Add the following code to the Form Module (Form1):

      Option Explicit
      Private Sub Form_Click()
         Dim myclass As New Class1
         Dim sum As Integer
         Dim prop As Integer

         ' Example of calling a method with CallByName
         ' equivalent to -- sum = myclass.Multiply(12, 12)
         sum = CallByName(myclass, "Multiply", VbMethod, 12, 12)
         MsgBox sum

         ' Example of a property let with CallByName
         ' equivalent to -- myclass.MyProperty = 5
         CallByName myclass, "MyProperty", VbLet, 5

         ' Example of a property get with CallByName
         ' equivalent to -- prop = myclass.MyProperty
         prop = CallByName(myclass, "MyProperty", VbGet)
         MsgBox prop
      End Sub

Run the Project and click on Form1. A message box displaying the number 144 and a message box displaying the number 5 are shown in succession.