Qt signal error : undefined reference to 'FramesEditor::setNewActiveFrame(Frame *)' ?

[high_flyer]

I don't have the time to look at the emit implmentation, but I don't think emit can do what your code is telling it.
As far as I know, emit needs a signature of an empty method defined as a signal (that moc then translates to calls in an meta object).

One why to do it is to wrap the signal emitting in your singleton:
Something like this:

void FramesEditor::emitSetNewActiveFrame(Frame *frame){
     emit setNewActiveFrame(frame);
}

void FramesEditor::emitSetNewActiveFrame(Frame *frame){
     emit setNewActiveFrame(frame);
}

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and in the using code:

void FrameManager::setCurrentActiveFrame(int frameID)
{
    qDebug()<<">>> frameManager.cpp : currentActiveFrame ID : "<<currentActiveFrame;
    Frame *activeFrame = frameBank[keyStartFrame];
 
    if(frameBank.contains(frameID)){
        currentActiveFrame = frameID;
        activeFrame = frameBank[currentActiveFrame];
    }
    qDebug()<<">>> frameManager.cpp : currentActiveFrame ID updated: "<<currentActiveFrame;
 
    //emit (FramesEditor::getInstance())->setNewActiveFrame(activeFrame); //causing error
     FramesEditor::getInstance()->emitSetNewActiveFrame(activeFrame);
}

void FrameManager::setCurrentActiveFrame(int frameID)
{
    qDebug()<<">>> frameManager.cpp : currentActiveFrame ID : "<<currentActiveFrame;
    Frame *activeFrame = frameBank[keyStartFrame];

    if(frameBank.contains(frameID)){
        currentActiveFrame = frameID;
        activeFrame = frameBank[currentActiveFrame];
    }
    qDebug()<<">>> frameManager.cpp : currentActiveFrame ID updated: "<<currentActiveFrame;

    //emit (FramesEditor::getInstance())->setNewActiveFrame(activeFrame); //causing error
     FramesEditor::getInstance()->emitSetNewActiveFrame(activeFrame);
}

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You will also need to update your connect().
But there is also a deisgn issue here.
You are emitting a signal defined in FramesEditor from FrameManager, which is possible as I have shown but points to a design flaw.
Since signals are only messages, they should be defined by the signaling object.
So I don't see why this signal is defined in FramesEditor and not in FrameManager.
That is probably the best line of action - move the signal to FrameManager since it is the class actually emitting the signal.

[keshav2010]

Thanks for pointing out the design flaw, and also updated connect to a newer syntax. That fixed the issue