I am trying to write a VBA macro to AutoFilter a table using the users input. I need the user to indicate the columns to filter and also the Criteria for that field. Therefore I thought to define a Sub with multiple optional arguments(parameters) to take users preference. My problem is how to check if an optional argument is supplied?
I understand that I can write a test for each parameter and then write a conditional statement for each possible option. But that doesn’t seem a smart way and am wondering if any one can suggest a solution. I should say that in the beginning we don’t know what’s the number of argument we expect to receive from the user.
Thanks for your responses.
A possibility would be to specify an absurd default. Then compare with the default.
Sub xyz( Optional p1 As String = "default_impossible_value")
If p1 = "default_impossible_value" Then
MsgBox "there_is_no_value_for_param_1"
End If
End Sub
Then extend it to any number of parameter you wish as an entry:
Sub xyz( Optional p1 As String = "default_impossible_value"_
,Optional p2 As String = "default_impossible_value"_
,Optional p3 As String = "default_impossible_value"_
...
)
If p1 = "default_impossible_value" Then
MsgBox "there_is_no_value_for_param_1"
End If
If p2 = "default_impossible_value" Then
MsgBox "there_is_no_value_for_param_2"
End If
If p3 = "default_impossible_value" Then
MsgBox "there_is_no_value_for_param_3"
End If
....
End Sub
Answer：
If the type of the variable is variant a solution would be to use IsMissing:
If IsMissing(arg) Then
MsgBox "missing parameter"
End If
Then if you expect string or number, just check the value:
Function func (Optional s as String, Optional n as Integer)
If s = "" Then
MsgBox "s is missing"
End If
If n = 0 Then
MsgBox "n is missing"
End
