How to send signal between other files in C++

w.tkm

Hello.

I want to send a signal from CppA to CppB, but I don't know how to do it.
How can I do this?

CppA

void CppA::sigSend(){
    emit sig();
}

CppB

CppB::CppB(QObject *parent): QObject(parent)
{
    CppA* cppA = new CppA(this);
    connect(cppA, &CppA::sig, this, &CppB::slotRecv);
}

void CppB::slotRecv()
{
    qDebug() << "OK";
}

KroMignon

@w-tkm said in How to send signal between other files in C++:

Also, CppA::sigSend is executed in one second cycle using Timer in QML.

I don't think so, you have declared cppA as a local variable in CppB constructor.
At constructor end, this variable will be destroyed, so it cannot generate any signal.

KroMignon

@w-tkm said in How to send signal between other files in C++:

I want to send a signal from CppA to CppB, but I don't know how to do it.
How can I do this?

It is not that complicated, but you should first take time to read at least how it works: https://doc.qt.io/qt-5/signalsandslots.html

If you still have trouble, explain us what did not work and you will got help.
Doing in reverse order will not help you.

w.tkm

@KroMignon
I'm asking because I couldn't figure it out after reading...
I tried changing some of the code, but it still doesn't work.

CppB::CppB()
{
    CppA cppA;
    connect(&cppA, &CppA::sig, this, &CppB::slotRecv);
}

Also, CppA::sigSend is executed in one second cycle using Timer in QML.

jsulm

@w-tkm said in How to send signal between other files in C++:

CppA cppA;

cppA is a local variable and is destroyed when CppB::CppB() finishes...

KroMignon

@w-tkm said in How to send signal between other files in C++:

Also, CppA::sigSend is executed in one second cycle using Timer in QML.

I don't think so, you have declared cppA as a local variable in CppB constructor.
At constructor end, this variable will be destroyed, so it cannot generate any signal.

w.tkm

@KroMignon
Thanks,I managed to make it work.
Finally, I realized that I need to connect at the CppA where the signal is sent.

CppA::CppA(QObject *parent): QObject(parent)
{
    cppB = new CppB();
    connect( this, &CppA::sig, cppB, &CppB::slotRecv);
}