Comments on: IsMissing

By: Stebain

Stebain — Mon, 13 Aug 2007 23:22:00 +0000

My only real issue with this example is... you don't provide an example!

There was enough here to remind me how to use it, but... I had used it plenty before and had just forgotten that it had to be a variant.

Had I not already known how to use it, I wouldn't have actually learned how to use the IsMissing.

By: Zach

Zach — Tue, 07 Aug 2007 00:54:00 +0000

One good reason to use a variant argument is to allow for flexibility is a general purpose function. I probably can't think of many examples of this, but one real world example I do have is a sub that creates and sends a message through Outlook. The declaration is this:

Sub Mailer(MailTo As String, Subject As String, Body As String, Optional MailCC As String, Optional MailBCC As String, Optional Attachments As Variant, Optional Receipt As Boolean)

I use the variant argument to accept either a string or an array of strings, to allow for flexibility when I drop in this module.

That said, I totally agree about the strong typing. I use variants as sparingly as possible, but they do come in handy from time to time.

By: fzz

fzz — Mon, 06 Aug 2007 19:06:00 +0000

This time with VB tags.

If IsMissing(OptionalString) Then
OptionalString = ""
ElseIf VarType(OptionalString <> 8) Then
Err.Raise . . .
Else
'it's a string - nothing more to do
End If

By: fzz

fzz — Mon, 06 Aug 2007 19:04:00 +0000

I don’t see the claimed problem. There is a potential problem: variants take more memory and slow down processing since it takes extra cycles to determine what type they currently contain.

However, strong typing is not a problem (provided you could live with runtime instead of compiletime errors). It COULD be handled in code, just like checking whether the optional variable is missing or not.

If IsMissing(OptionalString) Then
OptionalString = “”
ElseIf VarType(OptionalString <> Then
Err.Raise . . .
Else
‘it’s a string – nothing more to do
End If

By: Alex J

Alex J — Mon, 06 Aug 2007 14:02:00 +0000

I use the same technique as Tony (specified default)all the time, especially for functions called from VBA.

It also keeps the code more concise - I don;t have to verify ISMISSING to determine how to use the passed variable. Also useful when multiple optional values are passed.