Is there a way to pass a void function with any type and amount of arguments as an argument in a method and store it in a data member? (C++)

Question

I ran into a problem while passing a function as a parameter in a method. My problem is that I want to be able to pass any void function with any type and amount of arguments and then store it in a data member. What I currently do is an overload for a void function without arguments and an overload for a void function with a vector argument of type std::any and then add an extra parameter for the vector. Here is an example of what I did:

typedef void (*FunctionT1)();
typedef void (*FunctionT2)(std::vector<std::any>);

class ExampleClass {
public:
    void saveFunction(FunctionT1 f) {
        emptyFunction = f;
    }
    void saveFunction(FunctionT2 f, std::vector<std::any> args) {
        vectorFunction = f;
        vectorFunctionArgs = args;
    }
private:
    FunctionT1 emptyFunction;

    FunctionT2 vecotorFunction;
    std::vector<std::any> vectorFunctionArgs;
}

Now this works and I'm able to do what I want but it's clearly a pretty bad solution. Is there a way to do this in an other way? (I was thinking of template packs but couldn't figure out how those would work)

Answer 1

From what I understand, you want to call a function void(), where caller might register other function type with bind parameters. You might do it with std::function:

class ExampleClass {
public:
    void saveFunction(std::function<void()> f) {
        this->f = f;
    }
    void call() { f(); }
private:
    std::function<void()> f;
};

with usage

void foo();
void bar(std::vector<std::any>);

std::vector<std::any> v;

ExampleClass ex;

ex.SaveFunction(&foo); ex.call(); // foo();
ex.SaveFunction([&]() { bar(v); }); ex.call(); // bar(v);
// You might capture by copy/move if you prefer (instead of by reference)