Iterating a variadic argument?

[Josh]

Every example I can find online uses a chr*. You can't call ++ on an std::any. Does anyone know how to correctly iterate this to get all the arguments?:

	bool LuaComponent::CallMethod(const WString& name, const std::any& args...)
	{
		std::vector<std::any> v;

		auto vargs = va_list();
		va_start(vargs, args);

		while (args.has_value())
		{
			v.push_back(args);
			args++;//??? this does not compile
		}

		va_end(vargs);
		return CallMethod(name, v);
	}

 

[IceBurger]

What does the `std::any args` data look like?

 

EDIT: I think I was completely wrong about the solution this message used to show

[IceBurger]

Would doing 

args = va_arg(vargs, std::any);

instead of

args++

work?

[Josh]

Apparently not.  It's okay, I don't think I am going to use this anyways.

[Josh]

The C implementation of variadic functions is really bad. You have to specify the number of parameters, which makes it more code than just passing a vector.

[IceBurger]

edit: nvm, not even joking I thought it worked, but I built the wrong file. fml lmao. 🤡

 

edit 2:

nvm again. this works (tbh idek if this is what you were trying to do to begin with):

template <typename... Args>
std::vector<std::any> VariadicToVector(Args&&... args) {
	return {std::forward<Args>(args)...};
}

int main() {
	auto v = VariadicToVector(1, 'A', "hello", 2.8);
  
	std::cout << std::any_cast<char>(v[1]) << std::endl; // outputs 'A'
}

[IceBurger]

Looking back at your code, it appears that you wanted to exclude elements that don't have a value. This can be done like so:

template <typename... Args>
std::vector<std::any> VariadicToVector(Args&&... args) {
	std::vector<std::any> v;
  
	for (auto&& arg :
		 std::initializer_list<std::any>{std::forward<Args>(args)...}) {
		if (arg.has_value()) {
			v.emplace_back(std::forward<decltype(arg)>(arg));
		}
	}
  
	return v;
}

int main() {
	std::any a; // empty; aka has_value() == false

	auto v = VariadicToVector(1, a, 'A', "hello", 2.8);
	std::cout << std::any_cast<char>(v[1]) << std::endl; // outputs 'A', confirming exclusion
}

Don't you just love C++