Unable to add items when function called from other class?

[Christian Ehrlicher]

So my assumption is correct - the pointer is invalid and therefore the app is crashing.

[adalovegirls]

@Christian-Ehrlicher How can I make it valid when I need it, then?

[Christian Ehrlicher]

@adalovegirls said in Unable to add items when function called from other class?:

How can I make it valid when I need it, then?

I don't know your code - make sure to create a proper widget, don't delete it afterwards.

[kshegunov]

@adalovegirls said in Unable to add items when function called from other class?:

How can I make it valid when I need it, then?

Out of curiosity, is there a reason that everybody and their mother is a global variable?
Anyway, I peeked, and you're almost certainly calling updateWidgets() when there's no Debugger object created.
Piece of advice - fix this code pronto. Globals are nasty, everything global is everything nasty ... you get the idea ...

[adalovegirls]

@kshegunov No reason! I'm just a beginner who doesn't really know what they're doing. :)
And yes, I am aware now that I was calling updateWidgets() when Debugger had yet to be created, I'm asking how I can solve this in a more elegant way than calling it every mainLoop iteration:

void SDL2Widget::mainLoop() {
    debug = Debugger::getDebugContext();

    if (debug)
        debug->updateWidgets();
}

It works, but I'm sure it's not the best way to do it.

[kshegunov]

@adalovegirls said in Unable to add items when function called from other class?:

And yes, I am aware now that I was calling updateWidgets() when Debugger had yet to be created, I'm asking how I can solve this in a more elegant way than calling it every mainLoop iteration:

If you keep the Debugger as a pseudo-singleton (i.e. a glorified global), this is exactly how you do it.
Alternatively, you can enforce that a debugger is created before whatever widget by passing its address through the widget's constructor (and saving it in a member variable). Then you can't create a widget without first having a debugger and you don't get/check anything in the loop. If you're in the loop then Debugger has been passed to you/exists already.

[adalovegirls]

@kshegunov Alright. I guess I'll stick with the current method then, because I don't want it to be a requirement that the debugger is created before the emulator runs.

[kshegunov]

@adalovegirls said in Unable to add items when function called from other class?:

Alright. I guess I'll stick with the current method then, because I don't want it to be a requirement that the debugger is created before the emulator runs.

Then I suggest you put the pointer into the class and set it to the widget through a setter, instead of coupling the classes through the Debugger::getDebugContext or pass it through the constructor, but with a default value (of nullptr). As a rule of thumb you want to rely on as few application-global states (a.k.a. global variables) as possible.

[adalovegirls]

@kshegunov I don't know how to do that without an example...

[kshegunov]

https://www.geeksforgeeks.org/constructors-c/
also
https://www.w3schools.com/cpp/cpp_encapsulation.asp

[adalovegirls]

This post is deleted!

[adalovegirls]

@kshegunov Alright. I tried making a setter function in SDL2Widget, but in the header for it I'm getting the error Debugger has not been declared even though I have debugger.h included:

SDL2Widget.h

#ifndef SDL2WIDGET_H
#define SDL2WIDGET_H

#include "chip8.h"
#include "SDL.h"
#include "debugger.h"

#include <QDebug>
#include <QWidget>
#include <QTimer>
#include <vector>

class SDL2Widget : public QWidget
{
	Q_OBJECT    
public:
    SDL2Widget(QWidget* parent = nullptr);
	~SDL2Widget();
    static void loadRom(std::vector<unsigned char> rom);
    static void recKey(int key, bool state);
    static Chip8* getC8Context();
    static SDL2Widget* getSDLContext();
    void setDebugContext(Debugger* dbg);
};
#endif

SDL2Widget.cpp

void SDL2Widget::setDebugContext(Debugger* dbg) {
    debug = dbg;
}

I'm also getting the error no matching function for call to SDL2Widget::setDebugContext(Debugger*) when calling the setter from the Debugger class:

debugger.cpp

sdl2->setDebugContext(this);

[kshegunov]

You probably have a cyclic dependency. Forward declare the class(es) and include the headers in the source files only is the solution.