QVector at/operator[] and const
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[EDIT: split off "this thread":http://developer.qt.nokia.com/forums/viewthread/5340 of rickbkis as it's a similar, though different problem, Volker]
Hi guys, I'm not sure if mine is the same problem as rickbkis' but I wanted to try here first before creating a new thread.
I'm trying to plot a vector of floats with QGLWidget so I have created a vector first to put all my points in there:
@private: QVector<QVector3D> vertices;@
And a public function that receives data from an external widget:
@public:
void plot(float *data, int size){
for(int i=0; i<size; i++)
vertices.at(i).setY(data[i]);
updateGL();
}@
But I'm getting the following error:
passing 'const QVector3D' as 'this' argument of 'void QVector3D::setY(qreal)' discards qualifiers
Do you know where exactly is my mistake located and how should I sove it? Thanks for any help,
Boris -
It's the use of "QVector::at() ":http://doc.qt.nokia.com/4.7/qvector.html#at. The docs state clearly, that it returns a const reference:
@
const T & QVector::at ( int i ) const
@use
@
vertices[i]
@in order to get a non-const reference. Watch out, value(i) returns a value, not a reference!
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The same is true for other containers as well.