QXmlResultItems Class Reference

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

#include <qxmlresultitems.h>

Public Functions
QXmlItem	current () const
	Returns the current item. More...
bool	hasError () const
	If an error occurred during evaluation of the query, true is returned. More...
QXmlItem	next ()
	Returns the next result in the sequence produced by lazy evaluation of the associated query. More...
	QXmlResultItems ()
	Constructs an instance of QXmlResultItems. More...
virtual	~QXmlResultItems ()
	Destroys this instance of QXmlResultItems. More...

Properties
QScopedPointer< QXmlResultItemsPrivate >	d_ptr

Friends
class	QXmlQuery

Detailed Description

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

Note

This class or function is reentrant.

Since

4.4

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(), QXmlNodeModelIndex

Definition at line 57 of file qxmlresultitems.h.

Constructors and Destructors

QXmlResultItems()

QXmlResultItems::QXmlResultItems

(

)

Constructs an instance of QXmlResultItems.

Definition at line 86 of file qxmlresultitems.cpp.

                                 : d_ptr(new QXmlResultItemsPrivate())
{
}

~QXmlResultItems()

QXmlResultItems::~QXmlResultItems ( )

virtual

Destroys this instance of QXmlResultItems.

Definition at line 93 of file qxmlresultitems.cpp.

{
}

Functions

current()

QXmlItem QXmlResultItems::current

(

)

const

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.

Definition at line 131 of file qxmlresultitems.cpp.

{
    Q_D(const QXmlResultItems);

    if(d->hasError)
        return QXmlItem();
    else
        return d->current;
}

hasError()

bool QXmlResultItems::hasError

(

)

const

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

Returns false if query evaluation has been done.

Definition at line 148 of file qxmlresultitems.cpp.

{
    Q_D(const QXmlResultItems);
    return d->hasError;
}

next()

QXmlItem QXmlResultItems::next

(

)

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.

Definition at line 106 of file qxmlresultitems.cpp.

Referenced by QDeclarativeXmlQueryEngine::doQueryJob(), QDeclarativeXmlQueryEngine::doSubQueryJob(), and QDeclarativeXmlQueryEngine::getValuesOfKeyRoles().

{
    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();
    }
}

Friends and Related Functions

QXmlQuery

friend class QXmlQuery

friend

Definition at line 68 of file qxmlresultitems.h.

Properties

d_ptr

QScopedPointer<QXmlResultItemsPrivate> QXmlResultItems::d_ptr

private

Definition at line 70 of file qxmlresultitems.h.

Referenced by QXmlQuery::evaluateTo().

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The documentation for this class was generated from the following files:

• /src/xmlpatterns/api/qxmlresultitems.h
• /src/xmlpatterns/api/qxmlresultitems.cpp