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#include "qxmlresultitems.h"

#include "qxmlresultitems_p.h"

#include "qitem_p.h"

QT_BEGIN_NAMESPACE

/*!

  \class QXmlResultItems

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

  \reentrant

  \since 4.4

  \ingroup xml-tools

  QXmlResultItems presents the evaluation of an associated query as a

  sequence of \l{QXmlItem}{QXmlItems}. The sequence is traversed by

  repeatedly calling next(), which actually produces the sequence by

  lazy evaluation of the query.

  \snippet doc/src/snippets/code/src_xmlpatterns_api_qxmlresultitems.cpp 0

  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.

  \sa QXmlItem::isNode(), QXmlItem::isAtomicValue(), QXmlNodeModelIndex

 */

/*!

  Constructs an instance of QXmlResultItems.

 */

QXmlResultItems::QXmlResultItems() : d_ptr(new QXmlResultItemsPrivate())

{

}

/*!

  Destroys this instance of QXmlResultItems.

 */

QXmlResultItems::~QXmlResultItems()

{

}

/*!

  Returns the next result in the sequence produced by lazy evaluation

  of the associated query. When the returned QXmlItem is null, either

  the evaluation terminated normally without producing another result,

  or an error occurred. Call hasError() to determine whether the null

  item was caused by normal termination or by an error.

  Returns a null QXmlItem if there is no associated QXmlQuery.

 */

QXmlItem QXmlResultItems::next()

{

    Q_D(QXmlResultItems);

    if(d->hasError)

        return QXmlItem();

    try

    {

        d->current = QPatternist::Item::toPublic(d->iterator->next());

        return d->current;

    }

    catch(const QPatternist::Exception)

    {

        d->current = QXmlItem();

        d->hasError = true;

        return QXmlItem();

    }

}

/*!

  Returns the current item. The current item is the last item

  that was produced and returned by next().

  Returns a null QXmlItem if there is no associated QXmlQuery.

 */

QXmlItem QXmlResultItems::current() const

{

    Q_D(const QXmlResultItems);

    if(d->hasError)

        return QXmlItem();

    else

        return d->current;

}

/*!

  If an error occurred during evaluation of the query, true is

  returned.

  Returns false if query evaluation has been done.

 */

bool QXmlResultItems::hasError() const

{

    Q_D(const QXmlResultItems);

    return d->hasError;

}

QT_END_NAMESPACE