Nightmares with plugins

[KShots]

Hello all,

I'm having a considerable amount of trouble getting my plugins to work. Following the documentation (under the "How to Create Qt Plugins" section), I am following the low-level approach of creating plugins to extend my application through the use of QPluginLoader.

Currently, the whole mess compiles, but when I try to obtain an instance of my plugin, I get a NULL-pointer.

Here's what I've got:

The base plugin header:

#include <QObject>
#include <QList>
#include <QTcpSocket>
#include <QPluginLoader>
 
class QWorkspace;
 
/**
	@author Richard F. Ostrow Jr. <kshots@warfaresdl.com>
*/
class formBasePlugin : public QObject
{
Q_OBJECT
public:
	formBasePlugin(QObject * parent = 0);
	virtual ~formBasePlugin();
 
	int row();
 
	virtual const QString pluginName()const = 0;
	virtual void onActivate() = 0;
 
	QList <formBasePlugin *> listChildren;
	void unload(){emit removed();}
	static QTcpSocket socketServer;
	static QWorkspace * ws;
	QPluginLoader * PL;
protected:
signals:
	void removed();
public slots:
};
 
Q_DECLARE_INTERFACE(formBasePlugin, "evilrpg.warfaresdl/1.0")

#include <QObject>
#include <QList>
#include <QTcpSocket>
#include <QPluginLoader>

class QWorkspace;

/**
	@author Richard F. Ostrow Jr. <kshots@warfaresdl.com>
*/
class formBasePlugin : public QObject
{
Q_OBJECT
public:
	formBasePlugin(QObject * parent = 0);
	virtual ~formBasePlugin();
	
	int row();
	
	virtual const QString pluginName()const = 0;
	virtual void onActivate() = 0;
	
	QList <formBasePlugin *> listChildren;
	void unload(){emit removed();}
	static QTcpSocket socketServer;
	static QWorkspace * ws;
	QPluginLoader * PL;
protected:
signals:
	void removed();
public slots:
};

Q_DECLARE_INTERFACE(formBasePlugin, "evilrpg.warfaresdl/1.0")

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Then I've got the header for one of the plugins:

#include <formBasePlugin.h>
 
/**
	@author Richard F. Ostrow Jr. <kshots@warfaresdl.com>
*/
class pluginWhiteboard : public formBasePlugin
{
	Q_OBJECT
	Q_INTERFACES(formBasePlugin)
public:
	pluginWhiteboard(QObject * parent = 0);
	virtual ~pluginWhiteboard();
 
	virtual const QString pluginName()const{return tr("Whiteboard");}
	virtual void onActivate();
};

#include <formBasePlugin.h>

/**
	@author Richard F. Ostrow Jr. <kshots@warfaresdl.com>
*/
class pluginWhiteboard : public formBasePlugin
{
	Q_OBJECT
	Q_INTERFACES(formBasePlugin)
public:
	pluginWhiteboard(QObject * parent = 0);
	virtual ~pluginWhiteboard();
	
	virtual const QString pluginName()const{return tr("Whiteboard");}
	virtual void onActivate();
};

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... and the implementation of said plugin:

Q_EXPORT_PLUGIN2(plugins, pluginWhiteboard)
 
pluginWhiteboard::pluginWhiteboard(QObject * parent) : formBasePlugin(parent)
{
	setObjectName("pluginWhiteboard");
}
 
pluginWhiteboard::~pluginWhiteboard()
{
}
 
void
pluginWhiteboard::onActivate()
{
}

Q_EXPORT_PLUGIN2(plugins, pluginWhiteboard)

pluginWhiteboard::pluginWhiteboard(QObject * parent) : formBasePlugin(parent)
{
	setObjectName("pluginWhiteboard");
}

pluginWhiteboard::~pluginWhiteboard()
{
}

void
pluginWhiteboard::onActivate()
{
}

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My application successfully finds the plugin (I have checked this), but fails to load said plugin. Am I missing anything blatantly obvious? Thanks.

[jacek]

What is the name of a file that contains this plugin?

[dcurtis]

what system? windows or linux?

[KShots]

What is the name of a file that contains this plugin?

libplugins.so

what system? windows or linux?

Both (in the end, at least). Currently testing with unix.

[wysota]

Do you have more than one plugin in the "libplugins" lib? I don't think this is possible... AFAIR you can have only one plugin export macro per plugin.

[KShots]

Do you have more than one plugin in the "libplugins" lib? I don't think this is possible... AFAIR you can have only one plugin export macro per plugin.

I only have one "libplugins" plugin. This is my first shot at plugins (at least under Qt... I've used ld and libtool ld before), and I had a bit of a misunderstanding that I have not yet corrected. It will end up being libWhiteboard.

The name of the source file(s) are pluginWhiteboard.[h/cpp]

And also, because I forgot to post it, the contents of the .pro file for the plugin:

# Target is a library:  whiteboard
 
QT = network core
INCLUDEPATH += ../src
TARGET = whiteboard
DESTDIR = ../bin/plugins
CONFIG += release \
          warn_on \
          qt \
          plugin
TEMPLATE = lib
HEADERS += pluginWhiteboard.h
SOURCES += pluginWhiteboard.cpp

# Target is a library:  whiteboard

QT = network core
INCLUDEPATH += ../src
TARGET = whiteboard
DESTDIR = ../bin/plugins
CONFIG += release \
          warn_on \
          qt \
          plugin
TEMPLATE = lib
HEADERS += pluginWhiteboard.h
SOURCES += pluginWhiteboard.cpp

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[wysota]

I think the name you put into the Q_EXPORT_PLUGIN2 macro is wrong.