qthread to const qthread *

user4592357

i'm trying to learn about how qt deals with threads. here's the example i use from docs. i build using visual studio, and get the error mentioned in the title.

the example actually uses &workerThread in the first connect() but that gives bunch of unresolved externals

#include "QtGuiApplication2.h"
#include <QtWidgets/QApplication>

#include <QThread>

class Worker : public QObject {
	Q_OBJECT
		public slots:
	void doWork(const QString &param) {
		QString result = "Ready!";
		emit resultReady(result);
	}

signals:
	void resultReady(const QString &result);
};

class Controller : public QObject {
	Q_OBJECT
		QThread workerThread;
public:
	Controller() {
		Worker *worker = new Worker;
		worker->moveToThread(&workerThread);
		connect(workerThread, &QThread::finished, worker, &QObject::deleteLater);
		connect(this, &Controller::operate, worker, &Worker::doWork);
		connect(worker, &Worker::resultReady, this, &Controller::handleResults);
		workerThread.start();
	}
	~Controller() {
		workerThread.quit();
		workerThread.wait();
	}
public slots:
	void handleResults(const QString &);
signals:
	void operate(const QString &);
};

int main(int argc, char *argv[]) {
	
	QApplication a(argc, argv);
	
	Controller c;

	return a.exec();
}

VRonin

@user4592357 said in qthread to const qthread *:

the example actually uses &workerThread in the first connect()

Because the first argument must be a pointer so you have to pass the address of workerThread

but that gives bunch of unresolved externals

No, it's not due to that. can you post the error?

user4592357

@VRonin

Error	LNK2019	unresolved external symbol "public: void __cdecl Controller::handleResults(class QString const &)" (?handleResults@Controller@@QEAAXAEBVQString@@@Z) referenced in function "public: __cdecl Controller::Controller(void)" (??0Controller@@QEAA@XZ)	QtGuiApplication2	

C:\Users\...\Documents\Visual Studio 2017\Projects\QtGuiApplication2\QtGuiApplication2\main.obj	1	
Error	LNK1120	11 unresolved externals	QtGuiApplication2	

C:\Users\...\Documents\Visual Studio 2017\Projects\QtGuiApplication2\x64\Debug\QtGuiApplication2.exe	1	
Warning	MSB8017	A circular dependency has been detected while executing custom build commands for item "GeneratedFiles\Debug\main.moc". This may cause incremental build to work incorrectly.	QtGuiApplication2	C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\Common7\IDE\VC\VCTargets\Microsoft.CppCommon.targets	171	

Error	LNK2001	unresolved external symbol "public: static struct QMetaObject const Controller::staticMetaObject" (?staticMetaObject@Controller@@2UQMetaObject@@B)	QtGuiApplication2	C:\Users\...\Documents\Visual Studio 2017\Projects\QtGuiApplication2\QtGuiApplication2\main.obj	1	

Error	LNK2001	unresolved external symbol "public: static struct QMetaObject const Worker::staticMetaObject" (?staticMetaObject@Worker@@2UQMetaObject@@B)	QtGuiApplication2 C:\Users\...\Documents\Visual Studio 2017\Projects\QtGuiApplication2\QtGuiApplication2\main.obj	1	

Error	LNK2001	unresolved external symbol "public: virtual int __cdecl Controller::qt_metacall(enum QMetaObject::Call,int,void * *)" (?qt_metacall@Controller@@UEAAHW4Call@QMetaObject@@HPEAPEAX@Z)	QtGuiApplication2	C:\Users\...\Documents\Visual Studio 2017\Projects\QtGuiApplication2\QtGuiApplication2\main.obj	1	

Error	LNK2001	unresolved external symbol "public: virtual int __cdecl Worker::qt_metacall(enum QMetaObject::Call,int,void * *)" (?qt_metacall@Worker@@UEAAHW4Call@QMetaObject@@HPEAPEAX@Z)	QtGuiApplication2	C:\Users\...\Documents\Visual Studio 2017\Projects\QtGuiApplication2\QtGuiApplication2\main.obj	1	

Error	LNK2001	unresolved external symbol "public: virtual struct QMetaObject const * __cdecl Controller::metaObject(void)const " (?metaObject@Controller@@UEBAPEBUQMetaObject@@XZ)	QtGuiApplication2	C:\Users\...\Documents\Visual Studio 2017\Projects\QtGuiApplication2\QtGuiApplication2\main.obj	1	

Error	LNK2001	unresolved external symbol "public: virtual struct QMetaObject const * __cdecl Worker::metaObject(void)const " (?metaObject@Worker@@UEBAPEBUQMetaObject@@XZ)	QtGuiApplication2	C:\Users\...\Documents\Visual Studio 2017\Projects\QtGuiApplication2\QtGuiApplication2\main.obj	1	

Error	LNK2001	unresolved external symbol "public: virtual void * __cdecl Controller::qt_metacast(char const *)" (?qt_metacast@Controller@@UEAAPEAXPEBD@Z)	QtGuiApplication2	C:\Users\...\Documents\Visual Studio 2017\Projects\QtGuiApplication2\QtGuiApplication2\main.obj	1	

Error	LNK2001	unresolved external symbol "public: virtual void * __cdecl Worker::qt_metacast(char const *)" (?qt_metacast@Worker@@UEAAPEAXPEBD@Z)	QtGuiApplication2	C:\Users\...\Documents\Visual Studio 2017\Projects\QtGuiApplication2\QtGuiApplication2\main.obj	1	

Error	LNK2019	unresolved external symbol "public: void __cdecl Controller::operate(class QString const &)" (?operate@Controller@@QEAAXAEBVQString@@@Z) referenced in function "public: __cdecl Controller::Controller(void)" (??0Controller@@QEAA@XZ)	QtGuiApplication2	C:\Users\...\Documents\Visual Studio 2017\Projects\QtGuiApplication2\QtGuiApplication2\main.obj	1	

Error	LNK2019	unresolved external symbol "public: void __cdecl Worker::resultReady(class QString const &)" (?resultReady@Worker@@QEAAXAEBVQString@@@Z) referenced in function "public: __cdecl Controller::Controller(void)" (??0Controller@@QEAA@XZ)	QtGuiApplication2	C:\Users\...\Documents\Visual Studio 2017\Projects\QtGuiApplication2\QtGuiApplication2\main.obj	1

.pro file:

TEMPLATE = app
TARGET = QtGuiApplication2
DESTDIR = ../x64/Debug
QT += core widgets gui
CONFIG += debug
DEFINES += WIN64 QT_DLL QT_WIDGETS_LIB
INCLUDEPATH += ./GeneratedFiles \
    . \
    ./GeneratedFiles/Debug
DEPENDPATH += .
MOC_DIR += ./GeneratedFiles/debug
OBJECTS_DIR += debug
UI_DIR += ./GeneratedFiles
RCC_DIR += ./GeneratedFiles
include(QtGuiApplication2.pri)

VRonin

void handleResults(const QString &); has no body. you have to at least have a {}
moc does not support 2 Q_OBJECT marked classes in the same file. move each class in its own header

user4592357

@VRonin i did but still getting the same errors

mrjj

@user4592357
Make sure to clean build folder and rebuild all.

VRonin

And re-run qmake