I whant a plot that will show a nuber of curves with the ability to add/remove curves.
The first idea i got was to use a QHash to store information about attached curves. So this is an overview:
Qt Code: 
  1. class Plotter: public QwtPlot
  2. {
  3. public:
  4. 	Plotter( QObject parent = 0 );
  5. 	~Plotter();
  6. 	bool addCurve( QString curveId, QwtData *data );
  7. 	bool removeCurve( QString curveId );
  8. 	const QwtPlotCurve* curve( QString curveId );
  9. 	const QwtData* data( QString curveId );
  10. private:
  11. 	QMultiHash<QString, QwtPlotCurve*, QwtData* > curveHash;
  12. };
  13.  
  14. bool Plotter::addCurve( QString curveId, QwtData *data ) {
  15. 	if( !curveHash.contains( curveId ) ) return false;
  16. 	QwtPlotCurve * curve = new QwtPlotCurve;
  17. 	curve->setData(*data);
  18. 	curve->attach(this);
  19. 	curveHash.insert( curveId, curve, data );
  20. 	return true;
  21. }
  22.  
  23. bool Plotter::removeCurve( QString curveId ) {
  24. 	if( !curveHash.contains( curveId ) ) return false;
  25. 	curveHash.value( curveId ).curve->detach(this);
  26. 	delete curveHash.value( curveId ).curve;
  27. 	delete curveHash.value( curveId ).data;
  28. 	curveHash.remove( curveId );
  29. 	return true;
  30. }
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I like this code, but maybe there's a better design.