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

Last reviewed: October 30, 1995
Article ID: Q129868
The information in this article applies to:
  • 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.


Additional reference words: 4.00 vb4win vb4all
KBCategory: kbprg kbole kbcode
KBSubcategory: IAPOLE


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Last reviewed: October 30, 1995
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