[jawsscripts] Re: Represent null in a comparison
- From: "Andy B." <sonfire11@xxxxxxxxx>
- To: <jawsscripts@xxxxxxxxxxxxx>
- Date: Thu, 8 Nov 2012 10:22:45 -0500
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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