How to pass not variadic values to fmt::format?

Question

I'm playing with the great fmt C++ library to format strings more gracefully.

And I'd like to pass a non-variable arguments list to fmt::format. It could be a std::vector, or std::string, or whatever, but it will always match the format string.

So fmt::format works like:

std::string message = fmt::format("The answer is {} so don't {}", "42", "PANIC!");

But what I'd like is something like:

std::vector<std::string> arr;
arr.push_back("42");
arr.push_back("PANIC!");
std::string message = fmt::format("The answer is {} so don't {}", arr);

Is there a way / workaround to do so?

Answer 1

Add an extra layer, something like:

template <std::size_t ... Is>
std::string my_format(const std::string& format,
                      const std::vector<std::string>& v,
                      std::index_sequence<Is...>)
{
    return fmt::format(format, v[Is]...);
}


template <std::size_t N>
std::string my_format(const std::string& format,
                      const std::vector<std::string>& v)
{
    return my_format(format, v, std::make_index_sequence<N>());
}

Usage would be:

std::vector<std::string> arr = {"42", "PANIC!"};
my_format<2>("The answer is {} so don't {}", arr);

With operator ""_format you might have the information about expected size at compile time