How does one bind namespace prefixes when using QXmlQuery (Qt XQuery)?

Question

I'm attempting to use QXmlQuery to execute an XQuery expression against a document with a declared default namespace.

For discussion:

<?xml version="1.0" encoding="UTF-8"?>
<root xmlns="http://namespace.com/ns1">
    <node1 attr1="hi"/>
</root>

Now, I have the following to open and query against the document:

QFile temp("my.xml");
temp.open(QIODevice::ReadOnly | QIODevice::Text);

QXmlQuery query;
query.setFocus(&temp);

QXmlResultItems items;
query.setQuery("/root");

query.evaluateTo(&items);

In running this, 'items' never has data in it, since the document is namespaced. Of course, if I remove the default namespace declaration, 'items' does have the correct data, but I don't have that luxury.

I've tried changing the query to: "/prefix:root", and Qt barks a warning like:

No namespace binding exists for the prefix prefix in prefix:root

So namespace binding does exist! But where? I see QXmlNamePool, but it has no mutator methods. I can create a QXmlName with the pool from the query ala:

QXmlName name(query.namePool(), "prefix", "http://namespace.com/ns1");

But it doesn't change anything. I'm at a loss, other toolkits I have used have simple methods to bind prefixes to namespace URIs.

serge_gubenko · Accepted Answer · 2011-02-16 02:53:46Z

4

I believe if you would change your query to

...
QXmlResultItems items;
query.setQuery("declare default element namespace \"http://namespace.com/ns1\"; /root");
...

it should return the data.

hope this helps, regards

answered Feb 16, 2011 at 2:53

serge_gubenko

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5 Comments

Nick Veys Over a year ago

That works! That's absolutely horrible API on Qt's part, but it works. Thanks!

user357812 Over a year ago

@Nick Veys: This is an XQuery expression, not XPath.

Nick Veys Over a year ago

@Alejandro: Is there a better class to be using then? It claims XPath support, as it's a subset of XQuery.

user357812 Over a year ago

@Nick Veys: I would use XQuery/XPath 2.0 over any XPath 1.0 engine

Nick Veys Over a year ago

I can't disagree, however requirements tend to trump preference. Thanks for the help!

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