[jawsscripts] Re: Represent null in a comparison
- From: Jackie McBride <abletec@xxxxxxxxx>
- To: jawsscripts@xxxxxxxxxxxxx
- Date: Thu, 8 Nov 2012 08:38:05 -0700
Andy, always include hjconst.jsh & hjglobal.jsh at the top of any scripts.
On 11/8/12, Andy B. <sonfire11@xxxxxxxxx> wrote:
> That's what I thought. BTW, what is the required file to include to get the
> keyword Var? Doing
>
> Var
> Object vs_addon
> //or
>
> Globals
> Var
> Object vs_addon
>
> Either one results in an error. The first one reports that Var is an
> unexpected string, and the second one reports an unexpected string globals.
> Just doing:
>
> Include "hjconst.jss"
> Globals
> Object vs_addon
>
> Function AutoStartEvent()
> Vs_addon = GetObject("VS_JAWS.Connect")
> If !vs_addon then
> SayMessage(OTJAWS_MESSAGE, "The addon cannot be found!")
> EndIf
> EndFunction
>
> Compiles just fine, so I guess I don't understand the keyword Var and
> why/when it is used.
>
> -----Original Message-----
> From: jawsscripts-bounce@xxxxxxxxxxxxx
> [mailto:jawsscripts-bounce@xxxxxxxxxxxxx] On Behalf Of Andrew Hart
> Sent: Thursday, November 08, 2012 10:08 AM
> To: jawsscripts@xxxxxxxxxxxxx
> Subject: [jawsscripts] Re: Represent null in a comparison
>
> 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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--
Blame the computer--why not? It can't defend itself & occasionally
might even be the culprit
Jackie McBride
Ask Me Computer Questions at: www.pcinquirer.com
Jaws Scripting training materials: www.screenreaderscripting.com
homePage: www.abletec.serverheaven.net
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