Undefined references during build of plugin in Qt Creator

Question

I'm trying to create plugin for Qt Creator, so I simply selected new file or project/Libraries/QtCreator plugin. I've specified the sources for Qt Creator as well as build of Qt Creator. When I've tried to build it I'm getting the following three errors:

*C:\...\mypluginplugin.cpp:20: error:  
 undefined reference to `vtable for MyPlugin::Internal::MyPluginPlugin'*  //this is constructor
*C:\...\mypluginplugin.cpp:25: error:  
undefined reference to `vtable for MyPlugin::Internal::MyPluginPlugin'* //this is destructor  
    C:\...\mypluginplugin.hpp:13: error:  
   undefined reference to `MyPlugin::Internal::MyPluginPlugin::staticMetaObject' //when I double click   
on this error it moves me to my .hpp file to the Q_OBJECT macro:  

This is my code:

namespace MyPlugin {
namespace Internal {

class MyPluginPlugin : public ExtensionSystem::IPlugin
{
    Q_OBJECT// the last, third error moves me here

public:
    MyPluginPlugin();
    ~MyPluginPlugin();

    bool initialize(const QStringList &arguments, QString *errorString);
    void extensionsInitialized();
    ShutdownFlag aboutToShutdown();

private slots:
    void triggerAction();
};

} // namespace Internal
} // namespace MyPlugin

Any idea how to solve this problem?
//EDIT

#include "mypluginplugin.hpp"
#include "mypluginconstants.hpp"

#include <coreplugin/icore.h>
#include <coreplugin/icontext.h>
#include <coreplugin/actionmanager/actionmanager.h>
#include <coreplugin/actionmanager/command.h>
#include <coreplugin/actionmanager/actioncontainer.h>
#include <coreplugin/coreconstants.h>

#include <QAction>
#include <QMessageBox>
#include <QMainWindow>
#include <QMenu>

#include <QtPlugin>

using namespace MyPlugin::Internal;

MyPluginPlugin::MyPluginPlugin()
{
    // Create your members
}

MyPluginPlugin::~MyPluginPlugin()
{
    // Unregister objects from the plugin manager's object pool
    // Delete members
}

bool MyPluginPlugin::initialize(const QStringList &arguments, QString *errorString)
{
    // Register objects in the plugin manager's object pool
    // Load settings
    // Add actions to menus
    // Connect to other plugins' signals
    // In the initialize method, a plugin can be sure that the plugins it
    // depends on have initialized their members.

    Q_UNUSED(arguments)
    Q_UNUSED(errorString)

    QAction *action = new QAction(tr("MyPlugin action"), this);
    Core::Command *cmd = Core::ActionManager::registerAction(action, Constants::ACTION_ID,
                                                             Core::Context(Core::Constants::C_GLOBAL));
    cmd->setDefaultKeySequence(QKeySequence(tr("Ctrl+Alt+Meta+A")));
    connect(action, SIGNAL(triggered()), this, SLOT(triggerAction()));

    Core::ActionContainer *menu = Core::ActionManager::createMenu(Constants::MENU_ID);
    menu->menu()->setTitle(tr("MyPlugin"));
    menu->addAction(cmd);
    Core::ActionManager::actionContainer(Core::Constants::M_TOOLS)->addMenu(menu);

    return true;
}

void MyPluginPlugin::extensionsInitialized()
{
    // Retrieve objects from the plugin manager's object pool
    // In the extensionsInitialized method, a plugin can be sure that all
    // plugins that depend on it are completely initialized.
}

ExtensionSystem::IPlugin::ShutdownFlag MyPluginPlugin::aboutToShutdown()
{
    // Save settings
    // Disconnect from signals that are not needed during shutdown
    // Hide UI (if you add UI that is not in the main window directly)
    return SynchronousShutdown;
}

void MyPluginPlugin::triggerAction()
{
    QMessageBox::information(Core::ICore::mainWindow(),
                             tr("Action triggered"),
                             tr("This is an action from MyPlugin."));
}

Q_EXPORT_PLUGIN2(MyPlugin, MyPluginPlugin)

Answer 1

I figured out what happened. Ok, here is the solution for others - qtcreator simply didn't attach .hpp files to the project, yet there were created. After adding those .hpp files via add existing files, it builds fine now.