q3sqlcursor.cpp

奇趣公司比较新的qt/emd版本

        cur.update();
    }
    \endcode

    In the above example, a cursor is created on the 'prices' table
    and is positioned on the record to be updated. Then a pointer to
    the cursor's edit buffer is acquired using primeUpdate(). A new
    value is calculated and placed into the edit buffer with the
    setValue() call. Finally, an update() call is made on the cursor
    which uses the tables's primary index to update the record in the
    database with the contents of the cursor's edit buffer. Remember:
    all edit operations (insert(), update() and delete()) operate on
    the contents of the cursor edit buffer and not on the contents of
    the cursor itself.

    Note that if the primary index does not uniquely distinguish
    records the database may be changed into an inconsistent state.

    \sa setMode() lastError()
*/

int Q3SqlCursor::update(bool invalidate)
{
    if (d->editIndex.isEmpty())
        return 0;
    return update(d->editIndex, invalidate);
}

/*!
    \overload

    Updates the database with the current contents of the cursor edit
    buffer using the specified \a filter. Returns the number of
    records which were updated.
    For error information, use lastError().

    Only records which meet the filter criteria are updated, otherwise
    all records in the table are updated.

    If \a invalidate is true (the default), the cursor can no longer
    be navigated. A new select() call must be made before you can move
    to a valid record.

    \sa primeUpdate() setMode() lastError()
*/

int Q3SqlCursor::update(const QString & filter, bool invalidate)
{
    if ((d->md & Update) != Update) {
        return false;
    }
    int k = count();
    if (k == 0) {
        return 0;
    }
    
    // use a prepared query if the driver supports it
    if (driver()->hasFeature(QSqlDriver::PreparedQueries)) {
        QString fList;
        bool comma = false;
        int cnt = 0;
        bool oraStyle = driver()->hasFeature(QSqlDriver::NamedPlaceholders);
        for(int j = 0; j < k; ++j) {
            QSqlField f = d->editBuffer.field(j);
            if (d->editBuffer.isGenerated(j)) {
                if (comma) {
                    fList += QLatin1Char(',');
                }
                fList += f.name() + QLatin1String(" = ") + (oraStyle == true ? QLatin1String(":f") + QString::number(cnt) : QString(QLatin1Char('?')));
                cnt++;
                comma = true;
            }
        }
        if (!comma) {
            return 0;
        }
        QString str(QLatin1String("update ") + name() + QLatin1String(" set ") + fList);
        if (filter.length()) {
            str+= QLatin1String(" where ") + filter;
        }
        return applyPrepared(str, invalidate);
    } else {
        QString str = QLatin1String("update ") + name();
        str += QLatin1String(" set ") + toString(&d->editBuffer, QString(), QString(QLatin1Char('=')), QString(QLatin1Char(',')));
        if (filter.length()) {
            str+= QLatin1String(" where ") + filter;
        }
        return apply(str, invalidate);
    }
}

/*!
    Deletes a record from the database using the cursor's primary
    index and the contents of the cursor edit buffer. Returns the
    number of records which were deleted.
    For error information, use lastError().

    Only records which meet the filter criteria specified by the
    cursor's primary index are deleted. If the cursor does not contain
    a primary index, no delete is performed and 0 is returned. If \a
    invalidate is true (the default), the current cursor can no longer
    be navigated. A new select() call must be made before you can move
    to a valid record. For example:

    \code
    Q3SqlCursor cur("prices");
    cur.select("id=999");
    if (cur.next()) {
        cur.primeDelete();
        cur.del();
    }
    \endcode

    In the above example, a cursor is created on the 'prices' table
    and positioned to the record to be deleted. First primeDelete() is
    called to populate the edit buffer with the current cursor values,
    e.g. with an id of 999, and then del() is called to actually
    delete the record from the database. Remember: all edit operations
    (insert(), update() and delete()) operate on the contents of the
    cursor edit buffer and not on the contents of the cursor itself.

    \sa primeDelete() setMode() lastError()
*/

int Q3SqlCursor::del(bool invalidate)
{
    QSqlIndex idx = primaryIndex(false);
    if (idx.isEmpty())
        return del(qWhereClause(&d->editBuffer, d->nm, QLatin1String("and"), driver()), invalidate);
    return del(toString(primaryIndex(), &d->editBuffer, d->nm, QString(QLatin1Char('=')), QLatin1String("and")), invalidate);
}

/*!
    \overload

    Deletes the current cursor record from the database using the
    filter \a filter. Only records which meet the filter criteria are
    deleted. Returns the number of records which were deleted. If \a
    invalidate is true (the default), the current cursor can no longer
    be navigated. A new select() call must be made before you can move
    to a valid record. For error information, use lastError().

    The \a filter is an SQL \c WHERE clause, e.g. \c{id=500}.

    \sa setMode() lastError()
*/

int Q3SqlCursor::del(const QString & filter, bool invalidate)
{
    if ((d->md & Delete) != Delete)
        return 0;
    int k = count();
    if(k == 0) return 0;
    QString str = QLatin1String("delete from ") + name();
    if (filter.length())
        str+= QLatin1String(" where ") + filter;
    return apply(str, invalidate);
}

/*
  \internal
*/

int Q3SqlCursor::apply(const QString& q, bool invalidate)
{
    int ar = 0;
    if (invalidate) {
        if (exec(q))
            ar = numRowsAffected();
    } else if (driver()) {
        QSqlQuery* sql = d->query();
        if (sql && sql->exec(q))
            ar = sql->numRowsAffected();
    }
    return ar;
}

/*
  \internal
*/

int Q3SqlCursor::applyPrepared(const QString& q, bool invalidate)
{
    int ar = 0;
    QSqlQuery* sql = 0;

    if (invalidate) {
        sql = (QSqlQuery*)this;
        d->lastAt = QSql::BeforeFirst;
    } else {
        sql = d->query();
    }
    if (!sql)
        return 0;

    if (invalidate || sql->lastQuery() != q) {
        if (!sql->prepare(q))
            return 0;
    }

    int cnt = 0;
    int fieldCount = (int)count();
    for (int j = 0; j < fieldCount; ++j) {
        const QSqlField f = d->editBuffer.field(j);
        if (d->editBuffer.isGenerated(j)) {
            if (f.type() == QVariant::ByteArray)
                sql->bindValue(cnt, f.value(), QSql::In | QSql::Binary);
            else
                sql->bindValue(cnt, f.value());
            cnt++;
        }
    }
    if (sql->exec()) {
        ar = sql->numRowsAffected();
    }
    return ar;
}

/*!
  Executes the SQL query \a sql. Returns true of the cursor is
  active, otherwise returns false.
*/
bool Q3SqlCursor::exec(const QString & sql)
{
    d->lastAt = QSql::BeforeFirst;
    QSqlQuery::exec(sql);
    return isActive();
}

/*!
    Protected virtual function which is called whenever a field needs
    to be calculated. If calculated fields are being used, derived
    classes must reimplement this function and return the appropriate
    value for field \a name. The default implementation returns an
    invalid QVariant.

    \sa setCalculated()
*/

QVariant Q3SqlCursor::calculateField(const QString&)
{
    return QVariant();
}

/*! \internal
   Ensure fieldlist is synced with query.

*/

static QString qTrim(const QString& s)
{
    QString result = s;
    int end = result.length() - 1;
    while (end >= 0 && result[end].isSpace()) // skip white space from end
        end--;
    result.truncate(end + 1);
    return result;
}

/*! \internal
 */

void Q3SqlCursor::sync()
{
    if (isActive() && isValid() && d->lastAt != at()) {
        d->lastAt = at();
        int i = 0;
        int j = 0;
        bool haveCalculatedFields = false;
        for (; i < count(); ++i) {
            if (!haveCalculatedFields && d->infoBuffer[i].isCalculated()) {
                haveCalculatedFields = true;
            }
            if (QSqlRecord::isGenerated(i)) {
                QVariant v = QSqlQuery::value(j);
                if ((v.type() == QVariant::String) &&
                        d->infoBuffer[i].isTrim()) {
                    v = qTrim(v.toString());
                }
                QSqlRecord::setValue(i, v);
                if (QSqlQuery::isNull(j))
                    QSqlRecord::field(i).clear();
                j++;
            }
        }
        if (haveCalculatedFields) {
            for (i = 0; i < count(); ++i) {
                if (d->infoBuffer[i].isCalculated())
                    QSqlRecord::setValue(i, calculateField(fieldName(i)));
            }
        }
    }
}

/*!
    Returns the value of field number \a i.
*/

QVariant Q3SqlCursor::value(int i) const
{
    const_cast<Q3SqlCursor *>(this)->sync();
    return QSqlRecord::value(i);
}

/*! \internal
  cursors should be filled with Q3SqlFieldInfos...
*/
void Q3SqlCursor::append(const QSqlField& field)
{
    append(Q3SqlFieldInfo(field));
}

/*!
    Returns true if the field \a i is NULL or if there is no field at
    position \a i; otherwise returns false.

    This is the same as calling QSqlRecord::isNull(\a i)
*/
bool Q3SqlCursor::isNull(int i) const
{
    const_cast<Q3SqlCursor *>(this)->sync();
    return QSqlRecord::isNull(i);
}
/*!
    \overload

    Returns true if the field called \a name is NULL or if there is no
    field called \a name; otherwise returns false.

    This is the same as calling QSqlRecord::isNull(\a name)
*/
bool Q3SqlCursor::isNull(const QString& name) const
{
    const_cast<Q3SqlCursor *>(this)->sync();
    return QSqlRecord::isNull(name);
}

/*! \internal */
void Q3SqlCursor::setValue(int i, const QVariant& val)
{
    sync();
#ifdef QT_DEBUG
    qDebug("Q3SqlCursor::setValue(): This will not affect actual database values. Use primeInsert(), primeUpdate() or primeDelete().");
#endif
    QSqlRecord::setValue(i, val);
}

/*! \internal */
bool Q3SqlCursor::seek(int i, bool relative)
{
    bool res = QSqlQuery::seek(i, relative);
    sync();
    return res;
}

/*! \internal */
bool Q3SqlCursor::next()
{
    bool res = QSqlQuery::next();
    sync();
    return res;
}

/*!
    \fn Q3SqlCursor::previous()

    \internal
*/

/*! \internal */
bool Q3SqlCursor::prev()
{
    bool res = QSqlQuery::previous();
    sync();
    return res;
}

/*! \internal */
bool Q3SqlCursor::first()
{
    bool res = QSqlQuery::first();
    sync();
    return res;
}

/*! \internal */
bool Q3SqlCursor::last()
{
    bool res = QSqlQuery::last();
    sync();
    return res;
}

#endif