Hello,

i try to load a plugin into my application. I have followed the "Text Area" example from the book "C++ GUI Programming with Qt4" but my application refuses to load the plugin.

That's how i have defined the plugin interface:

Qt Code: 
  1. #ifndef INTERFACE_H
  2. #define INTERFACE_H
  3.  
  4. #include <QtPlugin>
  5.  
  6. class PluginInterface
  7. {
  8. public:
  9.     virtual ~PluginInterface() { }
  10.  
  11.     virtual QString pluginName();
  12. };
  13.  
  14. Q_DECLARE_INTERFACE(PluginInterface, "cops.demo.PluginInterface/1.0")
  15.  
  16. #endif
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Here is the code of the plugin:

header-file:
Qt Code: 
  1. #ifndef MYPLUGIN_H
  2. #define MYPLUGIN_H
  3.  
  4. #include <QString>
  5.  
  6. #include "myPlugin.h"
  7. #include "../pluginInterface.h"
  8.  
  9.  
  10. class MyPlugin : public QObject, public PluginInterface
  11. {
  12.  
  13.     Q_OBJECT
  14.     Q_INTERFACES(PluginInterface)
  15.  
  16. public:
  17.     QString pluginName();
  18.  
  19. };
  20.  
  21. #endif
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and source file:
Qt Code: 
  1. #include <QtGui>
  2. #include <iostream>
  3.  
  4. #include "myPlugin.h"
  5.  
  6. QString MyPlugin::pluginName()
  7. {
  8.     return "My Plugin Name";
  9. }
  10.  
  11. Q_EXPORT_PLUGIN2(myplugin, MyPlugin)
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I can compile the plugin and get a libmyPlugin.so in my plugin directory.

Here you can see how i try to load the plugin in my application:

Qt Code: 
  1. void MainWindow::loadPlugins()
  2. {
  3.     QDir pluginDir(QApplication::applicationDirPath());
  4.  
  5.     if (!pluginDir.cd("plugins"))
  6.         return;
  7.  
  8.     foreach (QString fileName, pluginDir.entryList(QDir::Files)) {
  9.         std::cout << qPrintable(fileName)  << "\n";
  10.         QPluginLoader loader(pluginDir.absoluteFilePath(fileName));
  11.         if (PluginInterface *interface = qobject_cast<PluginInterface *>(loader.instance())) {
  12.             interfaces.append(interface);
  13.             std::cout << qPrintable(interface->pluginName()) << "loaded \n";
  14.         } else {
  15.             std::cout << "not loaded!\n";
  16.         }
  17.     }
  18. }
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The program finds the plugin ("std::cout << qPrintable(fileName) << "\n";" shows the filename of the plugin) but the if statement is always false so that i end in the else-arm.

Do you have an idea what's wrong here?

Thanks a lot!