Problem with plugin signals/slots

[faldzip]

AFAIK your code won't compile because for me code like this:

QString str("asdasd");
std::cout << str;

QString str("asdasd");
std::cout << str;

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result in this:

error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'QString' (or there is no acceptable conversion)

so I don't know how do you achieved compilation, but you can tell me how to do it :]
next thing is that maybe you forgot CONFIG += console or sth. Try using:

#include <QDebug>
 
...
 
qDebug() << statusMsg;

#include <QDebug>

...

qDebug() << statusMsg;

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except for that everything should work in your code in my opinion

[DiamonDogX]

I don't actually have the "cout" statement in my code... it was there just as a generic line of code. So my code does actually compile . Put anything you want there... the point I was trying to illustrate is that it simply doesn't ever get there. I put break points, try to pop up message dialogs, etc. so I know it does not actually execute... thx.

[seim]

Hi,

try to add Q_OBJECT to the UpgradeInterface declaration. It works written in that way in my code, I hope it will help you.

have a nice day

[faldzip]

ok, I've done some research and I think, like my preposter, that you should add Q_OBJECT macro in interface declaration, and you should not redefine signal in implementation, just emit it.

[DiamonDogX]

Hmm when I add Q_OBJECT, now when I compile my UpgradePlugin project, I get:

Error 3 error LNK2001: unresolved external symbol "public: virtual struct QMetaObject const * __thiscall UpgradeInterface::metaObject(void)const " (?metaObject@UpgradeInterface@@UBEPBUQMetaObject@@ XZ) UpgradePlugin.obj UpgradePlugin
Error 4 error LNK2001: unresolved external symbol "public: virtual void * __thiscall UpgradeInterface::qt_metacast(char const *)" (?qt_metacast@UpgradeInterface@@UAEPAXPBD@Z) UpgradePlugin.obj UpgradePlugin
Error 5 error LNK2001: unresolved external symbol "public: virtual int __thiscall UpgradeInterface::qt_metacall(enum QMetaObject::Call,int,void * *)" (?qt_metacall@UpgradeInterface@@UAEHW4Call@QMetaOb ject@@HPAPAX@Z) UpgradePlugin.obj UpgradePlugin
Error 6 fatal error LNK1120: 3 unresolved externals ..\UpgradePlugin.dll UpgradePlugin

[DiamonDogX]

Hmm when I call emit from the class that implements UpgradeInterface (UpgradePlugin), no luck . Keep in mind UpgradePlugin is its own separate project (and produces a dll) and references the same UpgradeInterface.h file as the app (exe) project does... not that that helps, just reiterating...

Error 3 error LNK2019: unresolved external symbol "protected: void __thiscall UpgradeInterface::statusUpdate(class QString)" (?statusUpdate@UpgradeInterface@@IAEXVQString@@@Z) referenced in function "public: virtual bool __thiscall UpgradePlugin:erformUpgrade(void)" (?performUpgrade@UpgradePlugin@@UAE_NXZ) UpgradePlugin.obj UpgradePlugin
Error 4 error LNK2001: unresolved external symbol "public: virtual struct QMetaObject const * __thiscall UpgradeInterface::metaObject(void)const " (?metaObject@UpgradeInterface@@UBEPBUQMetaObject@@ XZ) UpgradePlugin.obj UpgradePlugin
Error 5 error LNK2001: unresolved external symbol "public: virtual void * __thiscall UpgradeInterface::qt_metacast(char const *)" (?qt_metacast@UpgradeInterface@@UAEPAXPBD@Z) UpgradePlugin.obj UpgradePlugin
Error 6 error LNK2001: unresolved external symbol "public: virtual int __thiscall UpgradeInterface::qt_metacall(enum QMetaObject::Call,int,void * *)" (?qt_metacall@UpgradeInterface@@UAEHW4Call@QMetaOb ject@@HPAPAX@Z) UpgradePlugin.obj UpgradePlugin
Error 7 fatal error LNK1120: 4 unresolved externals ..\UpgradePlugin.dll UpgradePlugin

[faldzip]

nmake clean + qmake again :]
this works for me:
interface.h:

#ifndef INTERFACE_H
#define INTERFACE_H
 
#include <QtPlugin>
 
class PluginInterface : public QObject
{
	Q_OBJECT
public:
	PluginInterface(QObject *parent) : QObject(parent) {}
	virtual void someMethod() = 0;
signals:
	void someSignal();
};
 
Q_DECLARE_INTERFACE(PluginInterface, "pl.faldzip.PluginInterface")
#endif // INTERFACE_H

#ifndef INTERFACE_H
#define INTERFACE_H

#include <QtPlugin>

class PluginInterface : public QObject
{
	Q_OBJECT
public:
	PluginInterface(QObject *parent) : QObject(parent) {}
	virtual void someMethod() = 0;
signals:
	void someSignal();
};

Q_DECLARE_INTERFACE(PluginInterface, "pl.faldzip.PluginInterface")
#endif // INTERFACE_H

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myplugin.h:

#ifndef MYPLUGIN_H
#define MYPLUGIN_H
 
#include "plugin1_global.h"
#include "interface.h"
 
class MyPlugin : public PluginInterface
{
	Q_OBJECT
	Q_INTERFACES(PluginInterface)
public:
	MyPlugin(QObject *parent = 0);
	void someMethod();
};
 
#endif // MYPLUGIN_H

#ifndef MYPLUGIN_H
#define MYPLUGIN_H

#include "plugin1_global.h"
#include "interface.h"

class MyPlugin : public PluginInterface
{
	Q_OBJECT
	Q_INTERFACES(PluginInterface)
public:
	MyPlugin(QObject *parent = 0);
	void someMethod();
};

#endif // MYPLUGIN_H

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myplugin.cpp:

#include "myplugin.h"
 
MyPlugin::MyPlugin(QObject *parent)
		: PluginInterface(parent)
{
}
 
void MyPlugin::someMethod()
{
	emit someSignal();
}
 
Q_EXPORT_PLUGIN2(myplugin, MyPlugin);

#include "myplugin.h"

MyPlugin::MyPlugin(QObject *parent)
		: PluginInterface(parent)
{
}

void MyPlugin::someMethod()
{
	emit someSignal();
}

Q_EXPORT_PLUGIN2(myplugin, MyPlugin);

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and this was one project (with pro file containing TEMPLATE = lib and CONFIG += plugin),
and second project - app project:
main.cpp:

#include <QtGui>
#include <QtCore>
#include <QtPlugin>
#include "interface.h"
 
class SomeClass : public QObject
{
	Q_OBJECT
public:
	SomeClass(PluginInterface *pi, QObject *parent = 0) : QObject(parent), m_pi(pi) { connect(m_pi, SIGNAL(someSignal()), SLOT(someSlot2())); }
public slots:
	void someSlot() { m_pi->someMethod(); }
	void someSlot2() { qDebug("someSlot2"); }
private:
	PluginInterface *m_pi;
};
 
int main(int argc, char *argv[])
{
	QApplication a(argc, argv);
	QPluginLoader loader(a.applicationDirPath() + QDir::separator() + "plugin1.dll");
	QObject *obj = loader.instance();
	PluginInterface *pi = qobject_cast<PluginInterface *>(obj);
	if (!pi)
	{
		qDebug("plugin error");
		return 1;
	}
	QPushButton pb("Button");
	SomeClass sc(pi, &pb);
	pb.connect(&pb, SIGNAL(clicked()), &sc, SLOT(someSlot()));
	pb.show();
	return a.exec();
}
 
#include "main.moc"

#include <QtGui>
#include <QtCore>
#include <QtPlugin>
#include "interface.h"

class SomeClass : public QObject
{
	Q_OBJECT
public:
	SomeClass(PluginInterface *pi, QObject *parent = 0) : QObject(parent), m_pi(pi) { connect(m_pi, SIGNAL(someSignal()), SLOT(someSlot2())); }
public slots:
	void someSlot() { m_pi->someMethod(); }
	void someSlot2() { qDebug("someSlot2"); }
private:
	PluginInterface *m_pi;
};

int main(int argc, char *argv[])
{
	QApplication a(argc, argv);
	QPluginLoader loader(a.applicationDirPath() + QDir::separator() + "plugin1.dll");
	QObject *obj = loader.instance();
	PluginInterface *pi = qobject_cast<PluginInterface *>(obj);
	if (!pi)
	{
		qDebug("plugin error");
		return 1;
	}
	QPushButton pb("Button");
	SomeClass sc(pi, &pb);
	pb.connect(&pb, SIGNAL(clicked()), &sc, SLOT(someSlot()));
	pb.show();
	return a.exec();
}

#include "main.moc"

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so it shows a button, and when I click on it, it's callingSomeClass::someSlot() which is calling PluginInterface::someMethod(), whis is emitting someSignal() connected to someSlot2() so the "someSlot2" appears on the screen.

[DiamonDogX]

Thanks for the help... finally got it!

One problem was the Q_OBJECT thing... but after adding that I got some link errors, as I mentioned. Basically I reorganized my projects so that the UpgradeInterface was in its own separate project (lib), and I had the plugin project and app project both reference that project. Works