It seems I can\'t find a way to include
in my header so Qt knows about the QLineSeries class.
Qt += cha
As I wrote the question I found the answer.
I was missing using namespace QtCharts;
in the header file.
Got the reference from: http://doc.qt.io/qt-5/qtcharts-index.html
If you want to avoid specifying the namespace, you can also declare your variable as:
QtCharts::QLineSeries *series;
With this solution you always have to prepend QtCharts::
, but you also know your scope and the origin of your calls.