resetting variables in excel vba - excel

Question

I am trying to build a model with VBA doing some work for me. Assume I have 4 variables - unit, lease start date, lease p.a, and alternative lease p.a. There are more, but that does not matter for my problem. VBA loops through each line and gets the value for unit i in respective column.
So, logically, I could declare unit as string, lease start date as date, lease p.a as single, and alternative lease p.a. as single. The problem I have is that I need to distinguish between empty entry and 0. The default numerical value is going to be 0. the distinction between 0 and empty is crucial. The only way I found to get around this is to declare everything as Variant and then check if the corresponding range is empty. If it is empty, then lease the Variant default value (Empty), otherwise assign the value.
I have a feeling that this is going to seriously affect my code performance. Ultimately, there will be lots of variables and I want to refer to those variables in the code. Like, if isempty(AltLease) = true then do one thing, otherwise something else.
I also find that I can not empty single or date variables(date is actually not a problem, since it drops to 1900). Can anyone suggest something?
Here is the code:
Dim tUnitName As Variant
Dim tNumberOfUnits As Variant
Dim tLeaseCurLeaseLengthDef as Variant
Dim tLeaseCurLeaseLengthAlt as Variant
Sub tenancyScheduleNew()
Dim lRow As Long
Dim i As Long
lRow = Sheet2.Cells(Rows.Count, 2).End(xlUp).Row
For i = 3 To lRow
reAssignVariables i
Next i
End Sub
Sub reAssignVariables(i As Long)
tAssetName = checkIfEmpty(i, getColumn("Sheet4", "tAssetName", 3))
tNumberOfUnits = checkIfEmpty(i, getColumn("Sheet4", "tNumberOfUnits", 3))
tLeaseCurLeaseLengthDef = checkIfEmpty(i, getColumn("Sheet4", "tLeaseCurLeaseLengthDef", 3))
tLeaseCurLeaseLengthDef = checkIfEmpty(i, getColumn("Sheet4", "tLeaseCurLeaseLengthAlt", 3))
End Sub
Function getColumn(sh As String, wh As String, colNo As Long) As Long
Dim refSheet As Worksheet
Dim rFound As Range
Set refSheet = Sheets(sh)
With refSheet
Set rFound = .Columns(1).Find(What:=wh, After:=.Cells(1, 1), LookIn:=xlValues, LookAt:=xlWhole)
On Error GoTo 0
If Not rFound Is Nothing Then
getColumn = rFound.Offset(0, colNo - 1).Value
Else
End If
End With
End Function
This is the way I am doing it now, which I think will slow the performance down. This is only small part of variables that I have made - there is going to be much more. I just need to understand how to construct it correctly in the first place. More specifically, if there is a value in tLeaseCurLeaseLengthAlt, then code should use that, alternatively, use default value.

Answer 1

You can't empty a variable of type integer, since empty is not an integer. If you have a variant variable which is currently of subtype integer you can reset it to empty:
Sub test()
Dim v As Variant
Debug.Print TypeName(v)
v = 1
Debug.Print TypeName(v)
v = Empty
Debug.Print TypeName(v)
End Sub
output:
Empty
Integer
Empty
Also, the performance hit of using variants might not be as great as you fear. An informal test:
Sub InformalTest(n As Long)
Dim i As Long, sum1 As Double
Dim j As Variant, sum2 As Variant
Dim start As Double, elapsed1 As Double, elapsed2 As Double
start = Timer
For i = 1 To n
sum1 = sum1 + 1#
Next i
elapsed1 = Timer - start
start = Timer
For j = 1 To n
sum2 = sum2 + 1#
Next j
elapsed2 = Timer - start
Debug.Print "Nonvariant time: " & elapsed1 & ", Nonvariant sum: " & sum1
Debug.Print "Variant time: " & elapsed2 & ", Variant sum: " & sum2
End Sub
Sample output:
InformalTest 1000000
Nonvariant time: 0.060546875, Nonvariant sum: 1000000
Variant time: 0.099609375, Variant sum: 1000000
InformalTest 10000000
Nonvariant time: 0.521484375, Nonvariant sum: 10000000
Variant time: 0.599609375, Variant sum: 10000000

Answer 2

Maybe you could create your own classes? Example for Single.
Class Single2
Private m_value As Single
Private m_hasValue As Boolean
Public Property Let Initialize(ByVal source As Range)
m_hasValue = False
m_value = 0
If source Is Nothing Then _
Exit Property
' add any checks you need to recognize the source cell as non-empty
' ... to distinguish between empty entry and 0
If Trim(source.Value) = "" Then _
Exit Property
If Not IsNumeric(source.Value) Then _
Exit Property
m_value = CSng(source.Value)
m_hasValue = True
End Property
Public Property Get Value() As Single
Value = m_value
End Property
Public Property Get HasValue() As Boolean
HasValue = m_hasValue
End Property
And use the class like this:
Module:
Dim lease As Single2
Set lease = New Single2
lease.Initialize = Range("a1")
If lease.HasValue Then
Debug.Print "lease has value ... " & lease.Value
Else
Debug.Print "lease hasn't value ... "
End If