Nothing (VB/VBScript constant) in AutoIt

[DaleHohm]

In nearly every case I've encountered, setting a COM object to the null string ("") produces the same result as as setting the same to the constant "Nothing" in VB/VBScript.

This is unfortunately not always true.

So, here is a way to make the Nothing value available in AutoIt:

Local $oVBS = ObjCreate("ScriptControl")
$oVBS.language = "VBScript"
Global Const $Nothing = $oVBS.eval("Nothing")
$oVBS = $Nothing

$Nothing is then available to use anywhere in your script.

Dale

Note: There are cases where nothing works like $Nothing. for others you may be able to use 0, "" or the Default keyword.

Edited June 28, 2008 by DaleHohm

[GEOSoft]

In nearly every case I've encountered, setting a COM object to the null string ("") produces the same result as as setting the same to the constant "Nothing" in VB/VBScript.

This is unfortunately not always true.

So, here is a way to make the Nothing value available in AutoIt:

Local $oVBS = ObjCreate("ScriptControl")
$oVBS.language = "VBScript"
Global Const $Nothing = $oVBS.eval("Nothing")
$oVBS = $Nothing

$Nothing is then available to use anywhere in your script.

Dale

Thanks Dale. This could come in handy.

[James]

Neat. Thanks!

[arcker]

Excellent !

as you said, setting "" is not always sufficient.

thx for the tip.

[martin]

In nearly every case I've encountered, setting a COM object to the null string ("") produces the same result as as setting the same to the constant "Nothing" in VB/VBScript.

This is unfortunately not always true.

So, here is a way to make the Nothing value available in AutoIt:

Local $oVBS = ObjCreate("ScriptControl")
$oVBS.language = "VBScript"
Global Const $Nothing = $oVBS.eval("Nothing")
$oVBS = $Nothing

$Nothing is then available to use anywhere in your script.

Dale

Can you give an example of where "" doesn't work the same as $Nothing?

I don't know anything about VB. Is Nothing a predefined constant in VB?

[DaleHohm]

One example is the activeconnection property used with some ADO objects. You'll know that "" doesn't work because you'll get an error and $Nothing does because you don't.

Yes, Nothing is a literal constant in VB/VBScript.

Dale

[Gigglestick]

I wonder if there are any plans to make this a part of AutoIt, such as a @Nothing macro or a keyword Nothing. If not, it would be very helpful to have it, or fix the "" problem.

[ptrex]

@all

Some of the objects accept the AU3 keyword

Default

for this.

Regards

ptrex

[GEOSoft]

@all

Some of the objects accept the AU3 keyword for this.

Regards

ptrex

And as Dale pointed out in the original post some will accept "". The keyword in both his post and yours is "some".

$Nothing should work in all instances.

[idbirch]

Unfortunately I seem to have found a case where none of the current methods for harnessing the 'Nothing' VB variable work. I'm porting a VB script which does a simple check on backup progress in Symantec Backup Exec System Recovery Manager 8.0.1. The original VB script looks like this:

Option Explicit

Dim oProgDlg

Set oProgDlg = createObject("Symantec.VProProgress.ProgressDlg")
Call oProgDlg.ShowProgress(Nothing,True,True,"")

And my AutoIt version currently like this:

Local $oVBS = ObjCreate("ScriptControl")
$oVBS.language = "VBScript"
Global Const $Nothing = $oVBS.eval("Nothing")
$oVBS = $Nothing

$oProgDlg = ObjCreate("Symantec.VProProgress.ProgressDlg")
$oProgDlg.ShowProgress($Nothing,True,True,"")

But it doesn't work, the Symantec app does nothing at all, no errors are produced either (which is exactly what happens when you replace 'Nothing' in the VB Script with anything else). In the AutoIt version, I've tried 0, "", Default, DIMing a variable with no value and passing that, and the method posted in this thread, nothing works. And when I say nothing works, I mean Nothing doesn't work

I'm thinking I will have to just call the poxy VB script externally but that's just dirty, any other suggestions?

Edited November 24, 2010 by idbirch

[James]

I'm thinking I will have to just call the poxy VB script externally but that's just dirty, any other suggestions?

One. Stop reviving old topics, this has been dead for two years.

Post in the General Help and Support forum.

[idbirch]

I thought it better to revive a relevant topic rather than start another about an already discussed one. Silly me.

[James]

I thought it better to revive a relevant topic rather than start another about an already discussed one. Silly me.

In most cases, yes. When the relative topic is 2 years+ old, no, it's not.