QXmlResultItems Class Reference
[QtXmlPatterns module]

Detailed Description

The QXmlResultItems class iterates through the results of evaluating an XQuery in QXmlQuery.

QXmlResultItems presents the evaluation of an associated query as a sequence of QXmlItems. The sequence is traversed by repeatedly calling next(), which actually produces the sequence by lazy evaluation of the query.

 QXmlQuery query;
 query.setQuery("<e/>, 1, 'two'");
 QXmlResultItems result;

 if (query.isValid()) {
     query.evaluateTo(&result);
     QXmlItem item(result.next());
     while (!item.isNull()) {
         // use item
         item = result.next();
     }
     if (result.hasError())
         /* Runtime error! */;
 }

An effect of letting next() produce the sequence by lazy evaluation is that a query error can occur on any call to next(). If an error occurs, both next() and current() will return the null QXmlItem, and hasError() will return true.

QXmlResultItems can be thought of as an "iterator" that traverses the sequence of query results once, in the forward direction. Each call to next() advances the iterator to the next QXmlItem in the sequence and returns it, and current() always returns the QXmlItem that next() returned the last time it was called.

Note: When using the QXmlResultItems overload of QXmlQuery::evaluateTo() to execute a query, it is advisable to create a new instance of this class for each new set of results rather than reusing an old instance.

See also QXmlItem::isNode(), QXmlItem::isAtomicValue(), and QXmlNodeModelIndex.

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