c++ meta programming example

enum_with_raw_string.hpp

#include <optional>
#include <string>
#include <type_traits>

/**
 @tparam T must be an Enum type.
 @tparam C converter must have `toString` and `fromString` static methods
 */
template<typename T,
         typename C,
         std::enable_if_t<std::is_enum<T>::value, bool> = true,
         std::enable_if_t<std::is_invocable_r<T, decltype(C::fromString), std::string>::value, bool> = true,
         std::enable_if_t<std::is_invocable_r<std::string, decltype(C::toString), T>::value, bool> = true>
class EnumString
{
    T mCase;
    std::string mRawValue;

public:
    EnumString<T>(const T enumCase)
    {
        mCase = enumCase;
        mRawValue = C::toString(enumCase);
    }
    /**
     When there is no enum type it should be still possible to set raw string.
     */
    EnumString<T>(const std::string& rawValue)
    {
        mRawValue = rawValue;
        mCase = C::fromString(rawValue);
    }

    virtual ~EnumString() = default;

    std::string rawValue() const { return mRawValue; }
    T value() const { return mCase; }
};