Howto access CVars from code?

Development Programming & Scripting
1

Hello!

I’ve been working with the examples given here: Console Variables in C++

But I’m still having a hard time wrapping my head around the usage of “FAutoConsoleVariableRef”.
I have two (actually more) classes from which I need to be able to determine the current value of a given CVar.

I’ve added the following code to lets say ‘weapon.cpp’:

static int32 DrawWeaponDebugLines = 0;
FAutoConsoleVariableRef CVARDrawWeaponDebugLines(TEXT("Game.DrawDebugWeapons"),DrawWeaponDebugLines,...);

I can now access the DrawWeaponDebugLines as expected and it updates when I change its value via the console at runtime, but of course only within ‘weapon.cpp’.

My thinking is, that whenever/wherever I ‘register’ a cvar, I should be able to ‘read’ it also from wherever and whenever, I want. Is this basic assumption correct?

In lets say ‘item.cpp’, Ive tried adding:

extern FAutoConsoleVariableRef CVARDrawWeaponDebugLines;
int32 MyVar = CVARDrawWeaponDebugLines->GetInt();

but that just gives me unresolved symbol errors at link time!
I’ve also tried using:

CVar = IConsoleManager::Get().FindConsoleVariable(TEXT("Game.DrawDebugWeapons"));"

but that always returns null/0 for CVar, as if I never registered the CVar (it does show up if I run the help command in the console, I can ‘browse’ to it and read my help text).

Am I totally misunderstanding something here? Most examples I’ve found just use CVars within the same cpp file, but surely this must be possible sowehow? Any suggestion? Thanks!

2

Instead of declaring the console variables in a source file, you could add some kind of container (be it a class, struct, or namespace) for them. Like this:

// Header file

class FCVars
{
public:
	static FAutoConsoleVariableRef DrawWeaponDebugLines;

private:
	static int32 DrawWeaponDebugLinesValue;
};


// Source file

int32 FCVars::DrawWeaponDebugLinesValue = 0;
FAutoConsoleVariableRef FCVars::DrawWeaponDebugLines(...);
3

I tested this just now by copying-pasting your CVar registration in one of my cpp files and placing the extern declaration into a different cpp file and I actually didn’t get any linker errors at all. It seemed at first glance like it should work and I think it should. Something else may be going on that is causing the linker error.