Vector of std::function with different signatures

Question

I have a number of callback functions with different signatures. Ideally, I would like to put these in a vector and call the appropriate one depending on certain conditions.

Answer 1

Not sure how useful this would be for you, it is based on boost::any, redundant parameters are ignored. You can add try...catch for boost::bad_any_cast to prevent crash in case of mismatch between arguments' and parameters' types. Though I think regular std::bind is a better choice.

DEMO

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

struct IGenericFunction
{
    virtual ~IGenericFunction() = default;

    virtual void call(boost::any a1 = boost::any{}
                    , boost::any a2 = boost::any{}
                    , boost::any a3 = boost::any{}
                    , boost::any a4 = boost::any{}) = 0;
};

template 
class GenericFunction : public IGenericFunction
{
public:
    GenericFunction(std::function f) : _f{ f } {}

    virtual void call(boost::any a1 = boost::any{}
                    , boost::any a2 = boost::any{}
                    , boost::any a3 = boost::any{}
                    , boost::any a4 = boost::any{}) override
    {
        call_func(std::make_tuple(a1, a2, a3, a4)
                , std::make_index_sequence{});
    }

private:            
    template 
    void call_func(Tuple t, std::index_sequence s)
    {
        _f(boost::any_cast<
                typename std::tuple_element::type
           >(std::get(t))...);
    }

    std::function _f;

    using Params = std::tuple;
};

template 
std::shared_ptr make_generic_function_ptr(void(*f)(Args...))
{
    return std::make_shared>(f);
}

void func1(const std::string& value)
{
    std::cout << "func1 " << value << std::endl;
}

void func2(const std::string& value, int min, int max)
{
    std::cout << "func2 " << value << " " << min << " " << max << std::endl;
}

int main()
{
    std::vector> functions;

    functions.push_back(make_generic_function_ptr(&func1));    
    functions.push_back(make_generic_function_ptr(&func2));

    for (auto f : functions)
    {
        f->call(std::string("abc"), 1, 2);
    }
}