QHash<QString, QVector<float> > iteration

Mike_newbye

Hi,

I have a
@QHash<QString, QVector<float> >@
and i want to loop it changing the values in the vectors like, skipping some header, like following:

@
string a = "Cluster";
const char b = a.c_str();
float new_value;
float old_value;
float min = getMinHash(qhash);
float max = getMaxHash(qhash);
QHashIterator<QString, QVector<float> > i(qhash);
while (i.hasNext())
{
i.next();
if(i.key().operator !=(b))
{
for(int j = 0; j<i.value().size(); j++)
{
old_value = i.value().at(j);
new_value = (old_value - min)/(max-min)(0.99-0.01) + 0.01;
i.value().replace(j, new_value);
}
qDebug() << i.value();
}
}
@

And I have the following error:
@C:\Qt\latest test\Prototype\Coordinate.cpp:264: error: passing 'const QVector<float>' as 'this' argument of 'void QVector<T>::replace(int, const T&) [with T = float]' discards qualifiers [-fpermissive]@

on this: @i.value().replace(j, new_value);@

Could you please help me fixing this?

Thanks in advance.

? Offline

According to the documentation, QHashIterator is defined as a const iterator, so the value associated with a given instance would also be const. If you're wanting to loop over all the items in a QHash, I'd suggest using the begin() and end() iterator methods found in the class.

Sample code:
@
typedef QHash<QString, QVector<float> > MyHash;
typedef MyHash::iterator MyIterator;

MyHash qhash;

for( int i = 0; i < 3; i++ )
{
QVector<float> fvector;
QString key( "key" );

if( i > 0 )
{
    fvector.fill( i, i + 1 );
}

key += QString::number( i );
qhash.insert( key, fvector );

}

for( MyIterator it = qhash.begin(); it != qhash.end(); it++ )
{
// print key
qDebug() << "key:" << it.key();

// get value
QVector<float>& fvector = it.value();

// print previous size
qDebug() << "  prev size:" << fvector.size();

// modify QVector contents by removing first item
if( !fvector.isEmpty() )
{
    fvector.removeFirst();
}

// print new size
qDebug() << "  new size:" << fvector.size();

}
@

Sample output:

@
key: "key0"
prev size: 0
new size: 0
key: "key1"
prev size: 2
new size: 1
key: "key2"
prev size: 3
new size: 2
@

? Offline

Mike_newbye:

Did you ever get your code to work?