How to return the keys of a map in a vector

[Rumo]

Hi,

my method has the following code:

const QVector<unsigned int> CLandTypes::getLandTypes()
{
    QVector<unsigned int> returnValue;
 
    for(QMap<unsigned int, CLandType>::iterator mapLandTypeIterator = (QMap<unsigned int, CLandType>::iterator)d->LandTypes.begin(); mapLandTypeIterator != (QMap<unsigned int, CLandType>::iterator)d->LandTypes.end();++mapLandTypeIterator)
    {
        returnValue.push_back(mapLandTypeIterator.key());
    }
    return returnValue;
}

const QVector<unsigned int> CLandTypes::getLandTypes()
{
    QVector<unsigned int> returnValue;

    for(QMap<unsigned int, CLandType>::iterator mapLandTypeIterator = (QMap<unsigned int, CLandType>::iterator)d->LandTypes.begin(); mapLandTypeIterator != (QMap<unsigned int, CLandType>::iterator)d->LandTypes.end();++mapLandTypeIterator)
    {
        returnValue.push_back(mapLandTypeIterator.key());
    }
    return returnValue;
}

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How can it be done in a better way?

Rumo

[stampede]

If you really need to have a QVector, then try this:

const QVector<unsigned int> CLandTypes::getLandTypes()
{
    return d->LandTypes.keys().toVector();
}

const QVector<unsigned int> CLandTypes::getLandTypes()
{
    return d->LandTypes.keys().toVector();
}

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But according to Qt docs:

For most purposes, QList is the right class to use. Its index-based API is more convenient than QLinkedList's iterator-based API, and it is usually faster than QVector because of the way it stores its items in memory. It also expands to less code in your executable.

[Lykurg]

Just as a side node: With toVector() you won't save so much, because it also expands to a loop. It's only a little bit more sophisticated:

Q_OUTOFLINE_TEMPLATE QVector<T> QList<T>::toVector() const
{
    QVector<T> result(size());
    for (int i = 0; i < size(); ++i)
        result[i] = at(i);
    return result;
}

Q_OUTOFLINE_TEMPLATE QVector<T> QList<T>::toVector() const
{
    QVector<T> result(size());
    for (int i = 0; i < size(); ++i)
        result[i] = at(i);
    return result;
}

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[stampede]

With toVector() you won't save so much

That's right, it's just to have simpler code, better would be not to use any conversion at all.