excel VBA byref argument passed to function not being changed - vba

Question

I have been struggling with this for a while and have found some related questions but none seem to solve my problem so it might just be my coding. The goal is to populate a form from a user defined data type (Customer) and then retrieve the information from the form back into the data object after the user has updated the form. When I run this code with IOType = "O" it works fine, the data elements are all put into the form. When I run it with IOType = "I" it reads the text from the form into the DataObjectOrType variable but the customer object that I sent in is not updated (i.e. CurCustomer.name and CurCustomer.territory are both = ""). The underlying data elements of CurCustomer are all strings if that matters. I have tried this as a sub and a function, with and without parentheses, with and without the byref but nothing seems to make a difference.
update - I have simplified some things and added some code below. Madgui, you are right that it works with a data type (sub CustomerFormIO2). It also works with just a couple of strings (sub CustomerFormIO3). I put the code from the Customer class module below too in case that helps. I have a feeling this isn't going to work. Could it have something to do with the Get and Let properties using intermediary variables? Is there any way to get this to work?
Thanks.
Private Type structCustomer
Name As String
Territory As String
Rep As String
End Type
Public Sub CustomerFormIO1()
Dim CurCustomer As Customer
Dim IOType As String
Set CurCustomer = New Customer
IOType = "I"
Call ObjectIO("X", CurCustomer.Name, IOType)
Call ObjectIO("Y", CurCustomer.Territory, IOType)
ObjectIO "Z", CurCustomer.Rep, IOType
End Sub
Public Sub CustomerFormIO2()
Dim CurCustomer As structCustomer
Dim IOType As String
IOType = "I"
Call ObjectIO("X", CurCustomer.Name, IOType)
Call ObjectIO("Y", CurCustomer.Territory, IOType)
ObjectIO "Z", CurCustomer.Rep, IOType
End Sub
Public Sub CustomerFormIO3()
Dim CurCustomerName As String
Dim CurCustomerTerritory As String
Dim CurCustomerRep As String
Dim IOType As String
IOType = "I"
Call ObjectIO("X", CurCustomerName, IOType)
Call ObjectIO("Y", CurCustomerTerritory, IOType)
ObjectIO "Z", CurCustomerRep, IOType
End Sub
Public Function ObjectIO(FormObject As String, ByRef DataObjectOrValue As Variant, Optional IOType As String) As Variant
If IOType = "I" Then
DataObjectOrValue = FormObject
Else '"O"
FormObject = DataObjectOrValue
End If
ObjectIO = True
End Function
Customer Class Module:
Private c_CustName As String
Private c_Rep As String
Private c_Territory As String
Public Property Get Name() As String
Name = c_CustName
End Property
Public Property Let Name(CName As String)
c_CustName = CName
End Property
Public Property Get Rep() As String
Rep = c_Rep
End Property
Public Property Let Rep(CRep As String)
c_Rep = CRep
End Property
Public Property Get Territory() As String
Territory = c_Territory
End Property
Public Property Let Territory(CTerritory As String)
c_Territory = CTerritory
End Property
Private Sub Class_Initialize()
c_CustName = ""
c_Rep = ""
c_Territory = ""
End Sub

Answer 1

Oddly, it works if you define your Customer class as a Type (= static structure ) :
Private Type structCustomer
Name As String
Territory As String
Rep As String
End Type
In your code change
Dim CurCustomer As Customer
by
Dim CurCustomer As structCustomer
and comment the line :
'Set CurCustomer = New Customer

Answer 2

(Old post, but adding this since there's no definitive answer here.)
This can be done by passing a reference to the full object CurCustomer, but not by passing the property directly. Properties are evaluated and passed as values whether or not ByRef is specified.
When passing a Customer object, you can add the property directly within the receiving function (DataObjectOrValue.Name), but doing so would require extra logic to handle multiple properties in the same function.
You can also pass the property name and use CallByName to keep the function flexible.
See the example below.
Public Sub CustomerFormIO4()
Dim CurCustomer As Customer
Dim IOType As String
Set CurCustomer = New Customer
IOType = "I"
Call ObjectIO("X", CurCustomer, "Name", IOType)
Call ObjectIO("Y", CurCustomer, "Territory", IOType)
ObjectIO "Z", CurCustomer, "Rep", IOType
End Sub
Public Function ObjectIO(FormObject As String, _
ByRef DataObjectOrValue As Variant, PropName As String, _
Optional IOType As String) As Variant
If IOType = "I" Then
CallByName DataObjectOrValue, PropName, VbLet, FormObject
Else '"O"
CallByName DataObjectOrValue, PropName, VbGet, FormObject
End If
ObjectIO = True
End Function
You can verify that the issue is not unique to user-defined classes by trying the same approach with a worksheet object:
Sub wsNameByRefTest()
Dim ws As Object
Set ws = Sheets.Add
ws.Name = "It failed!"
changeNameByRef ws.Name
End Sub
Sub changeNameByRef(ByRef wsName As String)
wsName = "It worked!"
End Sub
For reference, see this MSDN Article. It's officially documentation on VBScript, but I've tested in VBA, and all points in the article apply. (ByRef is the default for parameters in both, for example.) I could find no similar reference for VBA specifically.
ByRef Parameters Passed by Value
If the parameter is specified as ByRef, the argument can still be passed by value. This occurs if one of the following is true:
The argument is in parentheses, and the parentheses do not apply to the argument list.
The variable sent as an argument is in a class.
The argument being passed is not a variable, for example, 12.