How to Pass a UDT to an OLE Automation Server in VB 4.0

• Standard, Professional, and Enterprise Editions of Microsoft Visual Basic, 16-bit and 32-bit, for Windows, version 4.0

SUMMARY

This article shows by example how to pass a user-defined type (UDT) to an OLE Automation server in Visual Basic version 4.0.

MORE INFORMATION

A UDT cannot be passed to a public member function of an OLE Automation Server. This behavior is by design. However, it is possible to pass a UDT to a private member function or to declare a private variable of a user defined type within a class module. But because these are private, they cannot be accessed directly by an OLE Automation Controller or Client. Therefore, you need to pass each field of the UDT, element by element, or create a class with public variables corresponding to each field of the UDT.

Step-by-Step Example

There are two parts to this example - creating the OLE Automation Server and creating the OLE Automation Controller.

Part One: Create the OLE Automation Server

1. Start a new project in Visual Basic. Form1 is created by default.

2. Choose Class Module from the Insert menu. Class1 is created by default.

3. Add the following code to the General Declarations section of Class1:

   Private Type UDT

         age As Integer
         name As String
   

   End Type

   Private ClassUDT As UDT

   Public Sub GetUDTFields(age As Integer, name As String)

         ClassUDT.age = age
         ClassUDT.name = name
      End Sub
   
      Public Sub DispalyClassUDT()
      MsgBox "Hi! My Name is " & ClassUDT.name & ". I am " & _
         ClassUDT.age & " years old"
      End Sub
   
   

4. Set the following properties for Class1:

      Properties     Value
      -------------------------------------
      Instancing     2 - Creatable MultiUse
      Name           Class1
      Public         True
   
   

5. Choose Module from the Insert menu. Module1 is created by default.

6. Add the following code to the General Declarations section of Module1:

      Sub main()
   
      End Sub
   
   

7. Choose Options from the Tools menu, and in the Project Options, select

      Sub Main as the Startup Form and OLE Server as the StartMode.
   
   

8. The OLE Automation server is now ready. Press the F5 key to run the program, and then minimize it.

Part Two: Create the OLE Automation Controller

1. Start a new instance of Visual Basic.

2. Start a new project in Visual Basic. Form1 is created by default.

3. Add the following code to the General Declarations section of Form1:

   Private Type UDT

         age As Integer
         name As String
   

   End Type

4. Add the following code to the Form_Click event of Form1:

   Dim x As Object Dim MyUDT As UDT

   MyUDT.age = 25 MyUDT.name = "Joe" Set x = CreateObject("Project1.Class1") x.GetUDTFields MyUDT.age, MyUDT.name x.DispalyClassUDT

5. Press the F5 key to run the program. Click Form1. A message box will display the fields of the UDT passed element-by-element to the OLE Automation server.