c++ - Value disappears from QVector -


i have qmap qvector inside:

qmap<qstring, qmap<qgraphicsview*, qvector<float>>> graphs;

i'm trying execute code:

qvector<float>* graphvalues = &(graphs.values()[i - values.count()].values()[0]);  graphvalues->push_back(1234);  qdebug() << "=== debug messages ===\r\n"; qdebug() << "i - values.count() = " << - values.count(); qdebug() << "graphvalues = " << graphvalues; qdebug() << "*graphvalues = " << *graphvalues; qdebug() << "graphs = " << graphs; qdebug() << "graphs.values()[i - values.count()].values()[0] = " << graphs.values()[i - values.count()].values()[0];

it gives me output:

i - values.count() =  0 graphvalues =  0x2000e90 *graphvalues =  qvector(1234) graphs =  qmap(("tempgraph", qmap((qgraphicsview(0x1fb1920) ,  qvector() ) ) )) graphs.values()[i - values.count()].values()[0] =  qvector()

so, value? using pointer wait value in graphs, disappears.

qmap::values() method returns temporary object. cannot change original data, changing it. should use iterators, or qmap::operator[] somehow.


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