Enum reflection about refl-cpp HOT 2 CLOSED

Generally, I consider enum reflection to be out of scope, because there already are excellent libraries out there. I was going to suggest magic_enum just after reading the question title, but you say you know about it.

I haven't used magic_enum personally, but from looking at their readme, I do not see what more we could do in refl-cpp. It would be useful to know what limitations of magic_enum you are having trouble with.

from refl-cpp.

Okay. I understand.

It's not so much that there is a specific limitation of magic_enum that causes a problem for me. It's just that the approach seems too sub-optimal to me such that I don't want to build on top of it; even though it might actually work perfectly fine in practice.

Anyway, for future reference: I've tried a couple of different approaches to my issue and it appears that a constexpr array of pairs is sufficient for what I need. Reusing the example from above:

enum class ToneMapping {
#define IKAROS_ENUM_ToneMapping \
	IKAROS_ENUM_E(None) \
	IKAROS_ENUM_E(Uncharted2) \
	IKAROS_ENUM_E(ACES)
#define IKAROS_ENUM_E(_entry) _entry,
	IKAROS_ENUM_ToneMapping
#undef IKAROS_ENUM_E
};
constexpr std::array ToneMappingEntries{
#define IKAROS_ENUM_E(_entry) std::pair{ToneMapping::_entry, #_entry},
    IKAROS_ENUM_ToneMapping
#undef IKAROS_ENUM_E
};

This allows one to iterate over all entries, get the number of entries as a compile-time constant, and build more efficient lookup tables from it.

const etl::unordered_map<ToneMapping, std::string_view, ToneMappingEntries.size()> ToneMappingToStringLookup{
    ToneMappingEntries.begin(), ToneMappingEntries.end()};

std::string_view to_string(ToneMapping e)
{
	if (auto it = ToneMappingToStringLookup.find(e); it != ToneMappingToStringLookup.end()) {
		return it->second;
	} else {
		return "invalid";
	}
}

const auto ToneMappingFromStringLookup = [] {
	etl::unordered_map<std::string_view, ToneMapping, ToneMappingEntries.size()> lookup;
	for (const auto& entry : ToneMappingEntries) {
		lookup[entry.second] = entry.first;
	}
	return lookup;
}();

void from_string_impl(std::string_view input, std::optional<ToneMapping>& result)
{
	if (auto it = ToneMappingFromStringLookup.find(input); it != ToneMappingFromStringLookup.end()) {
		result = it->second;
	} else {
		result.reset();
	}
}

from refl-cpp.