HOWTO: Remote User-Defined Types

MORE INFORMATION

To pass a UDT as an argument, you must declare the UDT as Public in a Public class module. You must also use early binding to the UDT. For additional information, please see the article listed in the REFERENCES section.

A UDT can only be passed by reference. However, you can assign a UDT to a variant and pass the variant by value. This article shows both approaches to passing a UDT and how to check the variant to see if it holds the correct UDT type. You can also pass an array of UDT's in an argument.

For more information on passing arrays, please see the article listed in the REFERENCES section.

When remoting UDTs on Windows NT 4.0 you will need Service Pack 4 for Windows NT 4.0 if your ActiveX server is an EXE.

Sample Code

1. Create a project group with one Standard EXE and one ActiveX DLL project.
2. Change the names in the ActiveX DLL project to the following:
   

         Project name:  pjxUdtDll
         Class name:    clsUdtExample
   
   						

3. Add the following code to the clsUdtExample Class module:
   

         Option Explicit
   
         Public Type udtCustomer
            CustName As String
            CustID As Integer
         End Type
   
         Public Type udtEmployee
            EmpName As String
            EmpID As Integer
         End Type
   
         Public Sub PassUdtByRef(ByRef cust As udtCustomer)
         'Receive the UDT as a specific data type.
            Static i As Integer
            i = i + 1
            cust.CustName = StrReverse(cust.CustName)
            cust.CustID = i
   
         End Sub
   
         Public Function ReturnCustUdt() As udtCustomer
         'Return a UDT as a specific data type.
            Dim cust As udtCustomer
            cust.CustID = 99
            cust.CustName = "Bill"
            ReturnCustUdt = cust
         End Function
   
         Public Function WhichUdt(ByRef Guess As Variant)
         'Get a UDT stored in a Variant and then check to
         'see which UDT was passed.
            If TypeOf Guess Is udtCustomer Then
               MsgBox "you passed a Customer type"
            ElseIf TypeOf Guess Is udtEmployee Then
               MsgBox "you passed a Employee type"
            Else
               MsgBox "don't know what you passed"
            End If
         End Function
   
         Public Sub PassUdtByVal(ByVal Emp As Variant)
         'If you want to pass a UDT by value you must use
         'use a Variant data type.
            Static i As Integer
            If TypeOf Emp Is udtEmployee Then
               i = i + 1
               Emp.EmpID = i
               Emp.EmpName = StrReverse(Emp.EmpName)
               MsgBox "Emp value in class: " & Str(Emp.EmpID) _
                & " " & Emp.EmpName
            Else
               MsgBox "Unknow type"
            End If
          End Sub
   
   						

4. In the Standard EXE project, create a reference to the pjxUdtDll project. You can do this by selecting References from the Project menu.
5. In the Standard EXE project, add 4 command buttons and one check box to Form1.
6. Add the following code to Form1 in the Standard EXE project:
   

         Option Explicit
         Dim obj As pjxUdtDll.clsUdtExample
         Dim udtCust As pjxUdtDll.udtCustomer
         Dim udtEmp As pjxUdtDll.udtEmployee
   
         Private Sub Command1_Click()
         'Pass the UDT by reference.
            udtCust.CustID = 99
            udtCust.CustName = "Bob"
            obj.PassUdtByRef udtCust
            MsgBox "Before: CustID = 99 CustName = Bob" _
             & vbCrLf & "After: CustID = " & udtCust.CustID _
             & " CustName = " & udtCust.CustName
         End Sub
   
         Private Sub Command2_Click()
         'Get the value from the class.
            udtCust = obj.ReturnCustUdt
            MsgBox "CustID = " & udtCust.CustID _
             & " CustName = " & udtCust.CustName
         End Sub
   
         Private Sub Command3_Click()
         'Pass the type as a variant.
            Dim vTemp As Variant
            If Check1 Then
               vTemp = udtCust
            Else
               vTemp = udtEmp
            End If
            obj.WhichUdt vTemp
         End Sub
   
         Private Sub Command4_Click()
         'Pass the type in a variant by value.
            Dim vTemp As Variant
            udtEmp.EmpID = 99
            udtEmp.EmpName = "Bill"
            vTemp = udtEmp
            'You can pass the Variant or the UDT to the method.
            'Because the method takes a Variant as an argument
            'it will copy the UDT into the Variant.
            obj.PassUdtByVal udtEmp 'or obj.PassUdtByVal vTemp
            MsgBox "Emp value in Form: " & Str(udtEmp.EmpID) _
             & " " & udtEmp.EmpName
         End Sub
   
         Private Sub Form_Load()
            Check1.Caption = "Pass udtCustomer to WhichUdt method"
            Command1.Caption = "Pass UDT to Method"
            Command2.Caption = "Receive UDT from Method"
            Command3.Caption = "Pass UDT in Variant"
            Command4.Caption = "Pass UDT in Variant ByVal"
            Set obj = New pjxUdtDll.clsUdtExample
         End Sub
   
   						

7. Save and run the project group. Make sure that Project1 is the start up project.
8. Try clicking the different buttons. Also, try selecting and clearing the check box when you click the "Pass UDT in Variant" button.