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/****************************************************************************
**
** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the QtXmlPatterns module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the Technology Preview License Agreement accompanying
** this package.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights. These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
**
**
**
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/
#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.
\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.
\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
|
