Question

I have not used VB much but as far as I can tell scope works the same as in C#. The problem is, I’m using VB in MS Access so I am unsure if the rules are a bit different (though I assume they are not). The following code shows values being assigned to variables which have only been declared within the function parameters. Specifically looking at PurchaseOrderID, I am unsure as to how it is retaining its assigned value for use in the function proceeding it.

Function Create(SupplierID As Long, EmployeeID As Long, OrderID As Long, PurchaseOrderID As Long) As Boolean
    Dim rsw As New RecordsetWrapper
    If rsw.OpenRecordset("Purchase Orders") Then
        With rsw.Recordset
            .AddNew
            ![Supplier ID] = SupplierID
            If EmployeeID > 0 Then
                ![Created By] = EmployeeID
                ![Creation Date] = Now()
                ![Submitted By] = EmployeeID
                ![Submitted Date] = Now()
                ![Status ID] = Submitted_PurchaseOrder
            End If

            If OrderID > 0 Then
                ![Notes] = InsertString(PurchaseGeneratedBasedOnOrder, CStr(OrderID))
            End If
            If rsw.Update Then
                .Bookmark = .LastModified
                PurchaseOrderID = ![Purchase Order ID]
                Create = True
            End If
        End With
    End If
End Function


Function CreateLineItem(PurchaseOrderID As Long, ProductID As Long, UnitCost As Long, Quantity As Long) As Boolean
    Dim rsw As New RecordsetWrapper
    If rsw.OpenRecordset("Purchase Order Details") Then
        With rsw.Recordset
            .AddNew
            ![Purchase Order ID] = PurchaseOrderID
            ![Product ID] = ProductID
            ![Quantity] = Quantity
            ![Unit Cost] = UnitCost
            CreateLineItem = rsw.Update
        End With
    End If
End Function

Can someone give me some insight on this?

Answer 1

You can pass arguments to a VBA procedure by value or by reference. If you don’t specify either ByVal or ByRef in the procedure’s declaration, it defaults to ByRef. So the following two declarations are equivalent …

Function DoSomething(PurchaseOrderID As Long) AS Boolean
Function DoSomething(ByRef PurchaseOrderID As Long) AS Boolean

The key here is that ByRef allows changes to the argument within the procedure to be transmitted back to the caller.