can't emit a signal from a class, error: LNK2019: unresolved external symbol

solidtyper

i've created this class in VS2019 console app, but now i'm using my code in QT(UI app).

---General.h

#pragma once

#ifndef GENERAL_H
#define GENERAL_H
#define WIN32_LEAN_AND_MEAN

#include <string>
#include <iostream>
#include <Windows.h>
#include "server.h"

#include <QObject>
#include <QDebug>

class General : public QObject
{
    Q_OBJECT

signals:
    static void logSig();

public:	//functions
    static void outputMsg(std::string message, int msgType);
    static bool processParameter(std::string &command, std::string compCommand);

public:	//variables
    static bool cmdMode;
    static void log();
};

#endif // !GENERAL_H

and here is General.cpp

#include "general.h"

bool General::cmdMode = false;

void General::outputMsg(std::string message, int msgType)
{
   //when i remove this line it works
    emit General::logSig();
}

ERR: general.obj:-1: error: LNK2019: unresolved external symbol "public: static void __cdecl General::logSig(void)" (?logSig@General@@SAXXZ) referenced in function "public: static void __cdecl General::outputMsg(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,int)" (?outputMsg@General@@SAXV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@H@Z)

mchinand

Do you connect that signal to a slot elsewhere in your code? What does your connect statement look like? Specifically, what is your 'sender' object? I think it's unusual to have a signal be static.

solidtyper

@mchinand

i've worked with signals in this code in many times, you can emit a signal without connecting it and it doesn't throw this error.

i juts made it static so i can call it like this emit General::sig();, because the method i call it from is static.

this is how i connect it in Server.cpp:

General* general = new General();
QObject::connect(general, &General::sig, this, &Server::slot);

i removed static and called it from a non-static method. but nothing...

i guess i'll need to remake this class in Qt since even when i try to General* general = new General(); make a pointer to it it throws a similar error.

mchinand

@solidtyper said in can't emit a signal from a class, error: LNK2019: unresolved external symbol:

VS2019 console app

I'm not sure what you mean by this, but have you run moc on this file (or more likely, have it run automatically if you have a Qt .pro file or CMakeLists.txt file)?

JoeCFD

@solidtyper signals and slots are instance dependent in connect. You do not make them static.

solidtyper

@mchinand

what i meant is that it might have something under the hood, IDK but it's acting very different. but i'm noob at this i might be wrong.

anyhow. i deleted that class definetly and add the properties directly to the thread i tried to send the signal to.

it was only for categorizing methods, nothting else.

thank you BTW