Q185700: HOWTO: Remote User-Defined Types
Article: Q185700
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:6.0
Operating System(s):
Keyword(s): kbVBp600 kbGrpDSVBDB
Last Modified: 11-JAN-2001
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The information in this article applies to:
- Microsoft Visual Basic Professional Edition for Windows, version 6.0
- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0
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SUMMARY
=======
Visual Basic 6.0 allows you to have a User-defined type (UDT) as an argument or
return type of public properties and methods in an ActiveX code component. This
article shows some examples of the different ways you can pass or receive a UDT.
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.
REFERENCES
==========
For more information on early binding, please see the following articles in the
Microsoft Knowledge Base:
Q184898 : PRB: Can't Use Late Binding When Server Method Uses UDT
Q186423 : HOWTO: Return and Assign Arrays with Visual Basic 6.0
Q187922 : PRB: Passing a UDT To Or From an ActiveX EXE may Fail on NT
(c) Microsoft Corporation 1998. All Rights Reserved.
Contributions by Brian Combs, Microsoft Corporation
Additional query words: kbActiveX kbDSupport kbdse kbVBp kbVBp600
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Keywords : kbVBp600 kbGrpDSVBDB
Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB600Search kbVBA600 kbVB600
Version : WINDOWS:6.0
Issue type : kbhowto
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