Hi, I'm writing a program that uses plugins to extend it. I followed the examples in QT. But when I run the application it gives the error: symbol lookup error: /home/cquiros/MyApplication/plugins/libtnkbasicplugins.so: undefined symbol: _ZN16tnkBasicPolygons13createPolygonE7QString.

From the error I can see that the problem is in the function createPolygon. This fuction is private for the plugin.

If I remove the private function createPolygon. The application works just fine.

Any idea what I am doing wrong?

Many thanks.

Here is the code:

tnkinterfaces.h
Qt Code: 
  1. #ifndef TNKINTERFACES_H
  2. #define TNKINTERFACES_H
  3.  
  4. #include <QtPlugin>
  5. #include "tnkdelegatorfactory.h"
  6.  
  8. class QIcon;
  9.  
  10. class tnkPolygonInterface
  11.  {
  12.  public:
  13.      virtual ~tnkPolygonInterface() {}
  14.      virtual QStringList pluginNames() const = 0;
  15.      virtual QList<QIcon> pluginIcons() = 0;
  16.      virtual tnkPolygonSymbol* constructNewItem(const QString &pluginName, bool inDesignMode) = 0;
  17.      virtual tnkPolygonSymbol* loadItemFromData(const QString &pluginName, QByteArray &data, bool inDesignMode) = 0;
  18.  };
  19.  
  20. Q_DECLARE_INTERFACE(tnkPolygonInterface,"com.personal.MyApplication.tnkPolygonInterface/1.0")
  21.  
  22. #endif // TNKINTERFACES_H
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tnkbasicplugins.h
Qt Code: 
  1. #ifndef TNKBASICPLUGINS_H
  2. #define TNKBASICPLUGINS_H
  3.  
  4. #include <QtGui>
  5. #include <QObject>
  6. #include <src/tnkinterfaces.h>
  7.  
  8. class tnkBasicPolygons : public QObject, public tnkPolygonInterface
  9. {
  10.     Q_OBJECT
  11.     Q_INTERFACES(tnkPolygonInterface)
  12. public:
  13.     QStringList pluginNames() const;
  14.     QList<QIcon> pluginIcons();
  15.     tnkPolygonSymbol* constructNewItem(const QString &pluginName, bool inDesignMode);
  16.     tnkPolygonSymbol* loadItemFromData(const QString &pluginName, QByteArray &data, bool inDesignMode);
  17. private:
  18.     QPolygonF createPolygon(QString polygonType);
  19. };
  20.  
  21. #endif // TNKBASICPLUGINS_H
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in the .h createPolygon(QString polygonType) is private and not declared in the interfaces.

tnkbasicplugins.cpp
Qt Code: 
  1. #include "tnkbasicplugins.h"
  2.  
  3.  
  4. QStringList tnkBasicPolygons::pluginNames() const
  5. {
  6.     return QStringList() << tr("Box");
  7. }
  8.  
  9.  
  10. QList<QIcon> tnkBasicPolygons::pluginIcons()
  11. {
  12.     QList<QIcon> result;
  13.     QImage image;
  14.     QPainter painter(&image);
  15.  
  16.     // Create a 32x32 representation of the box
  17.     // and appends it to the list of icons
  19.     scene.setSceneRect(QRectF(0,0,101,101));
  20.     scene.addPolygon(createPolygon("Box"));
  21.     scene.render(&painter);
  22.     image.scaledToHeight(32);
  23.     image.scaledToWidth(32);
  24.     result.append(QIcon(QPixmap::fromImage(image)));
  25.  
  26.  
  27.     return result;
  28. }
  29.  
  30. tnkPolygonSymbol* tnkBasicPolygons::constructNewItem(const QString &pluginName, bool inDesignMode)
  31. {
  32.     tnkPolygonSymbol *result;
  33.     result = new tnkPolygonSymbol(0,0,inDesignMode); //Must change
  34.     if (pluginName == tr("Box"))
  35.     {
  36.         QPolygonF sqPolygon;
  37.         sqPolygon << QPointF(-100, -100) << QPointF(100, -100)
  38.                                << QPointF(100, 100) << QPointF(-100, 100)
  39.                                << QPointF(-100, -100);
  40.         result->setPolygon(createPolygon("Box"));
  41.  
  42.         //Need to see how to save data!
  43.  
  44.     }
  45.     return result;
  46. }
  47.  
  48. tnkPolygonSymbol* tnkBasicPolygons::loadItemFromData(const QString &pluginName, QByteArray &data, bool inDesignMode)
  49. {
  50.     tnkPolygonSymbol *result;
  51.     result = new tnkPolygonSymbol(0,0,inDesignMode); //Must change
  52.     if (pluginName == tr("Box"))
  53.     {
  54.  
  55.         result->setPolygon(createPolygon("Box"));
  56.  
  57.         //Need to see how to save data!
  58.  
  59.     }
  60.     return result;
  61. }
  62.  
  63.  
  64. QPolygonF createPolygon(QString polygonType)
  65. {
  66.     QPolygonF sqPolygon;
  67.     if (polygonType == "Box")
  68.     {
  69.         sqPolygon << QPointF(-100, -100) << QPointF(100, -100)
  70.                            << QPointF(100, 100) << QPointF(-100, 100)
  71.                            << QPointF(-100, -100);
  72.     }
  73.     return sqPolygon;
  74. }
  75.  
  76. Q_EXPORT_PLUGIN2(tnk_basicpolygons, tnkBasicPolygons)
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