XML Check if a node exists.

[AutoitMike]

I looked for information how how to test that a node exists on this forum and found the following:

#include <_XMLDomWrapper.au3>

$sXMLFile = "C:\XMLtest.xml"

$result = _XMLFileOpen($sXMLFile)
If $result = 0 Then
    MsgBox(0,"", "Error opening " & $sXMLFile)
    Exit
EndIf

$sXPath = "//Parent/Child"

$nodeArray = _XMLSelectNodes($sXPath)

if $nodeArray[0] > 0 Then
    MsgBox(0,"", "Service node found")
    ;MsgBox(0,"",$nodeArray [0])
Else
    MsgBox(0,"", "Service node NOT found")
EndIf

This in fact works, however, I have an extensive application already running reading / changing and cloning nodes using a different way of opening and using an XML file:

#include <_XMLDomWrapper.au3>

Local $oXML = ObjCreate("Microsoft.XMLDOM")
$oXML.load("C:\test.xml")

;IF...this Xpath exists, then a message box appears with the number of nodes.
;IF... this xpath does not exist, then an error is produced, "0" is not returned.

MsgBox(0,"","Count = " & $oXML.SelectNodes('/Parent/Child').length)

;Then when I am done doing the rest of my modifications, I use this to save the file:
$oXML.save("C:\test.xml")

You would think that this would work, but it does not:

$NodeArray=$oXML.SelectNodes("/parent/Child")

VarGetType reports that $Nodearray is an object when there is no such Xpath.

I cant find anything about an Array function in the MS documentation. I would like to test for non existent nodes without re inventing the wheel.

Thanks in advance

 

[Danp2]

Not sure that I understand the issue. Can't you just check the object's length property to verify if the node was found?

$NodeArray=$oXML.SelectNodes("/parent/Child")

If $NodeArray.length Then
    ; do more processing here
EndIf

 

[AutoitMike]

The problem occurs when the checked node does not exist.

That is what I want to test for.

If the node does not exist, then Autoit crashes, an error is raised and the program stops.

In the first example _XMLSelectNodes("xpath") creates an array whether or not any node exists. If no node exists, an array is created, however, with zero elements.

If I insert the line in my program

$nodeArray = _XMLSelectNodes($sXPath)

 

It fails, $NodeArray is not created.

 

[Danp2]

It works as expected In my tests. For example, the following uses the same file you provided in an earlier thread --

Local $oXML = ObjCreate("Microsoft.XMLDOM")
$oXML.load("CloneRPT.hr4")

testXpath("//ReportInfo/Service") ; exists
testXpath("//ReportInfo/noService") ; non-existent

Func testXpath($sXpath)
    $NodeArray=$oXML.SelectNodes($sXpath)
    MsgBox(0, $sXpath,"VarGetType = " & VarGetType($NodeArray) & @CRLF & "Count = " & $NodeArray.length)
EndFunc

 

[Nine]

@Danp2  I believe OP has an old version of the COM XML object.  In a previous thread, he was struggling too with boolean parameter and he needed to send it in string instead of a real boolean.  This must be another collateral issue of its old version.

@AutoitMike  Try using IsArray function

Edited April 27, 2022 by Nine

[Danp2]

@NineThanks for jumping in on this thread. I saw that prior post and I suspected the same thing about different versions of the XML object.

@AutoitMikeI'm guessing that you are using an older OS (ie: Windows 7). Are you able to test on Win10 or 11?

[AutoitMike]

I'm using Win7.

I'll try "IsArray"

[AutoitMike]

Holy cow,

Figured it out.

Local $oXML = ObjCreate("Microsoft.XMLDOM") 
$oXML.Load("C:\File.xml")

;Xpath Exists--$N > 0
$N=$oXML.SelectNodes("//Parent/Child").length

;Xpath does not Exist--$N =0
$N=$oXML.SelectNodes("//Parent/yyChildxx").length

I just realized that I needed to add ".length"

$N is never an array.

Thanks again----