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scriptstopper

Testing for Null/empty variable

10 posts in this topic

How is everyone?

Stuck on detecting if a variable is blank.

If $Variablename has no value, has not been defined, then do ....

In the head it's:

If $Variable = Null Then

Ideas?

Thanks.


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To check if a variable has been declared use the If IsDeclared("variablename") function. If the variable you're looking for is called $variable, use "variable" in the function. To see if the variable contains nothing in it, use If $Variable = "".


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#3 ·  Posted (edited)

Do you want a detecting function like this ?

Global $_A = '', $_B = 0, $_C = ' ', $_D = 0.5

ConsoleWrite ( "Is $_A Null : " & _IsVarIsNull ( $_A ) & @Crlf )
ConsoleWrite ( "Is $_B Null : " & _IsVarIsNull ( $_B ) & @Crlf )
ConsoleWrite ( "Is $_C Null : " & _IsVarIsNull ( $_C ) & @Crlf )
ConsoleWrite ( "Is $_D Null : " & _IsVarIsNull ( $_D ) & @Crlf )
Exit

Func _IsVarIsNull ( $_Var )
    If Not $_Var Then 
        Return True 
    Else
        Return False
    EndIf
EndFunc
Edited by wakillon

AutoIt 3.3.14.2 X86 - SciTE 3.6.0WIN 8.1 X64 - Other Example Scripts

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Do you want a detecting function like this ?

Global $_A = '', $_B = 0, $_C = ' ', $_D = 0.5

ConsoleWrite ( "Is $_A Null : " & _IsVarIsNull ( $_A ) & @Crlf )

ConsoleWrite ( "Is $_B Null : " & _IsVarIsNull ( $_B ) & @Crlf )

ConsoleWrite ( "Is $_C Null : " & _IsVarIsNull ( $_C ) & @Crlf )

ConsoleWrite ( "Is $_D Null : " & _IsVarIsNull ( $_D ) & @Crlf )

Exit

Func _IsVarIsNull ( $_Var )

If Not $_Var Then

Return True

Else

Return False

EndIf

EndFunc

In AutoIt much better solution than:

If Not somevar Then
    something
Else
    somethingelse
EndIf

is:

If somevar Then
    somethingelse
Else
    something
EndIf

@JohnOne, VarGetType is irrelevant. That function shows type (vt) of the variant holding the value of the variable.


♡♡♡

.

eMyvnE

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#6 ·  Posted (edited)

But is it safe to say that all autoit variables start their life as a string type?

EDIT:

Sorry scriptstopper, we are all being terribly rude.

I'm fine, although I'm having a bit of trouble with my colon, nothing to worry about though, thanks for asking.

You?

Edited by JohnOne

AutoIt Absolute Beginners    Require a serial    Pause Script    Video Tutorials by Morthawt   ipify 

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#9 ·  Posted (edited)

;)

We're allowed a little bit of a giggle I hope.

Maybe, maybe not.

To answer that question of yours from the above - probably not. It depends if the variable is initialized.

This is String type (VT_BSTR):

Local $Var

This is Int32 (VT_I4)

Local $Var = 4

If internally AutoIt would make VT_BSTR and then change its type to VT_I4 and then assign the value, it would make one step more than it should because it always starts with VT_EMPTY as that's the result of variant initialization.

So, logically it would be to start with VT_EMPTY (initialization) and then depending on the script code changing type to what's needed.

Edited by trancexx

♡♡♡

.

eMyvnE

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What is confusing me, is what autoit classes the variable type as.

I know you said vargettype was irrelevant but i would have expected that function to to be the judge of that very question.

Local $var is seen as a string before it is initialzed, and then converted when assigned a value be that an object or a int.

I cant speak about autoits internal enviroment, but in the scripting enviroment, it must start its life as string since there is no null.

Im pretty crap at explaining myself, sorry.


AutoIt Absolute Beginners    Require a serial    Pause Script    Video Tutorials by Morthawt   ipify 

Monkey's are, like, natures humans.

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