I've been looking through the archives, and reading the API, and I'm
curious about something that must be a simple thing.
I am using a small xml file to store some numbers (ints and floats).
I am trying to use an xpath to extract them.
So, I started this way (sort of pseudo C code):
doc = xmlParseFile(filename);
xpathCtx = xmlXPathNewContext(doc);
xpath = "/path/to/element";
xpathObj = xmlXPathEvalExpression(xpathExpr, xpathCtx);
content = xmlNodeGetContent(xpathObj->nodesetval->nodeTab[0]);
This gives me the content of the element as an xmlChar* (it works -
if it shouldn't then I made a typo). Of course since the element
content is to be used as a number (int, float) then I have to further
convert it from a string to a number.
So, looking for something more elegant, I came across the function:
xmlXPathCastToNumber(xpathObj)
This works fine returning a double. But I also came across the function:
xmlXPathStringEvalNumber(xpathObj->stringval);
or
xmlXPathStringEvalNumber(xpathObj->floatval);
and it does not work. What I mean is, it doesn't work for my purposes
- it returns null, and herein lies my question. I'm gathering that
xmlXPathCastToNumber is essentially the same thing as the pseudo C
code; that is, the mechanism to get to the content is via the
xmlNodeSetPtr. Whereas, xmlXPathStringEvalNumber does not work
because I am accessing that part of the xmlXPathObject structure that
has never been filled out... ?
Can someone please discuss this and correct my thinking? How exactly
to use xmlXPathStringEvalNumber(), and when/why?
Stefan Jeglinski
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