Graham, here's the basic approach (assuming your XML is in the variable 'tXML'):
put revXMLCreateTree(tXML,false,true,false) into tTreeID
put "/gpx/trk/trkseg/trkpt[1]" into tNode -- the brackets identify
the instance of "trkpt" to work with
put revXMLAttribute(tTreeID, tNode,"lon") into tLonValue
put revXMLNodeContents(tTreeID,(tNode & "/ele")) into tEleValue
put tLonValue && "/" && tEleValue
>> 2.128369 / 169.623637
So to work with the third instance of "trkpt", you'd do:
put "/gpx/trk/trkseg/trkpt[3]" into tNode
Hope this helps,
Ken
> On Oct 25, 2020, at 12:21 PM, Graham Samuel via use-livecode
> <[email protected]> wrote:
>
> I feel stupid, but even with Sarah Reichelt’s help, there are very very
> simple things I can’t do with the LC XML functions. My current problem is
> this:
>
> I have a series of XML files which are in fact .gpx files - a collection of
> GPS coordinates representing a route on the Earth’s surface. There are
> thousands of files around which I can use as test data, so I don’t have to
> roll my own. Taking just one of these examples, I can do the following in LC
>
> 1. Get the user to find the file and download it
>
> 2. Check it’s a .gpx file
>
> 3. Turn it into an LC XML data structure with an integer ID
>
> 4. Find out how many child nodes there are.
>
> Then it all goes wrong, because I don’t seem to be able to address the
> individual nodes. This is obviously needed for further progress, in functions
> like revXMLFirstChild and revXMLNodeContents.
>
> I just don’t know what format to use. Sarah’s tutorial doesn’t help because
> her data structure is too simplified.
>
> If you’re still with me, this is what the beginning of a typical file looks
> like:
>
>> <?xml version="1.0" encoding="UTF-8"?>
>> <gpx xmlns="http://www.topografix.com/GPX/1/1"; creator="Digital Crow"
>> version="1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
>> xsi:schemaLocation="http://www.topografix.com/GPX/1/1
>> http://www.topografix.com/GPX/1/1/gpx.xsd";>
>> <metadata />
>> <trk>
>> <trkseg>
>
>> <trkpt lat="43.319729" lon="2.128369">
>> <ele>169.623637</ele> </trkpt>
>
>> <trkpt lat="43.319731" lon="2.128375">
>> <ele>169.744722</ele> </trkpt>
>
>> <trkpt lat="43.319731" lon="2.128375">
>> <ele>169.744722</ele> </trkpt>
>
>> <trkpt lat="43.319731" lon="2.128388">
>> <ele>169.266626</ele> </trkpt>
>>
> etc - there may sometimes be thousands of these “trkpt” elements.
>
> So, suppose I want to get the first instance of the “lon” attribute into a
> local variable. How do I address the first <trk> node etc in order to do it?
> I have attempted various common-sense methods, but none work.
>
> This must be child’s play to a lot of people, just not me.
>
> Hoping for some guidance.
>
> Graham
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Ken Ray
Sons of Thunder Software, Inc.
Email: [email protected]
Website: https://www.sonsothunder.com
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