VB Automation of Visual C++ Server Using OBJ1.OBJ2.prop Syntax

WINDOWS        | WINDOWS NT

The information in this article applies to:

• The Microsoft Foundation Classes included with:

      - Microsoft Visual C++ for Windows, versions 1.5, 1.51, 1.52
      - Microsoft Visual C++, 32-bit Edition, versions 2.0, 2.1, 2.2,
        4.0, 4.1
  

SUMMARY

It is often necessary to access properties within nested objects exposed by OLE Automation. The Visual Basic syntax is:

   OBJ1.OBJ2.Property

MORE INFORMATION

The following steps demonstrate how to create a Visual C++ OLE Automation server that allows Visual Basic to use the OBJ1.OBJ2.Property syntax.

Steps to Create the Visual C++ OLE Automation Server

1. Create an AppWizard-generated project called AutoServ with OLE Automation enabled.

2. Once the project has been generated, start ClassWizard.

3. Click the OLE Automation tab.

4. Click the Add Class button, enter the following values, and then click Create Class:

      Class Name:    nested
      Class Type:    CCmdTarget
      Check:         OLE Automation
   
   

5. Click the ClassWizard's OLE Automation tab. Set the Class Name to nested, click the Add Property button, enter the following values, and then click OK:

   External Name: Value

      Type:          long
   
   

6. Change the Class Name in ClassWizard to CAutoServDoc. If you are prompted to save changes, click Yes. Then click the Add Method button, enter the following values, and click OK:

   External Name: Nested

      Return Type:   LPDISPATCH
   
   

7. Click OK to accept the additions created by ClassWizard.

8. Open the project's AutoServDoc.h file, and add the following line to the beginning of the file:

      #include "nested.h"
   
   

9. To the same file, add a public member variable m_nested of type nested. A pointer mechanism could have been used to maintain the nested class; however, for this example, the chosen method will automatically create and destroy the nested object within the Documents constructor and destructor respectively.

10. Open the project's nested.h file, and modify the class so that the

        constructor and destructor are public methods.
    

11. Open the projects AutoServDoc.cpp file, and modify the Nested Method

        as follows:
    

        LPDISPATCH CAutoServDoc::Nested()
        {
           //TODO: Add your dispatch handler code here
           return m_nested.GetIDispatch(TRUE);
        }
    

12. Build the project, and then run AutoServ.exe to register the server.

Steps to Test the Server in Visual Basic

1. Start a new project in Visual Basic that will be used to test the OLE Automation server.

2. On the View menu, click Code.

3. In the Object combo box, select (general).

4. Enter the following code:

   Dim Server As object

5. Select Form in the Object combo box. Modify the Sub procedure as follows:

      Sub Form_Load ()
         Set Server = CreateObject("autoserv.document")
         Server.Nested.Value = 10
         x = Server.Nested.Value
      End Sub
   
   

6. Add x and Server.Nested.Value to the Visual Basic watch window, so that you can observe the changes while stepping into the Visual Basic program.