[jawsscripts] Re: Represent null in a comparison
- From: Andrew Hart <ahart@xxxxxxxxxxxxx>
- To: jawsscripts@xxxxxxxxxxxxx
- Date: Thu, 08 Nov 2012 12:08:17 -0300
The usual way of doing this in JAWS script is to do something like this:
Var
Object oMyObject
If !oMyObject Then
SayString("Error! The object does not exist.")
EndIf
This has always worked for me. I'm guessing you could also compare the
object var with the return from the Null function, e.g.,
if oMyObject==Null() Then
SayString("Error! The object does not exist.")
EndIf
Though the first method is neater and faster imho. Don't waste your
time doing other kinds of comparisons. The only comparison that makes
sense of Object variables is zero/non-zero.
The following should also work in theory, but I have never tried it. It
depends how clever/fussy that Script compiler type-checking/type-casting is.
if oMyObject!=0 Then
SayString("Error! The object does not exist.")
EndIf
btw, I should mention that null and empty are not the same concepts in
VB. Is Nothing is testing if an object variable or database entry is
not set to any value, indicating an undefined object pointer or db
entry. vbEmpty, on the other hand, applies to strings and is equivalent
to "". In JAWS script, if you want to check if a String is empty, it is
best to use
If Length(mystring)==0 Then
...
EndIf
Although in mor recent versions of JAWS (since JAWS 13 if I remember
correctly), the following should work:
If mystring=="" Then
...
EndIf
It is safer to test the length of the string as this works in all
versions of JAWS.
Hth,
Andrew.
On 8/11/2012 10:50 AM, Andy B. wrote:
> In most languages, you can test for a null, nothing in VB, or empty object
> by doing this:
>
>
> C#: if (!vs_addon) {do something if it doesn't exist}
>
> VB: if vs_addon is nothing then do something if it doesn't exist end if
>
>
>
> How would you do this in a jaws script?
>
>
>
>
>
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