试图让我的枚举等同于 std::error_code

Question

我是 going through std::error_code and am now trying to make my list of error enums equivalent to std::error_code. I'm following what's on this 教程，但由于某种原因我无法让它工作，我总是以错误 No viable conversion from 'my_project::my_error' to 'std::error_code'.

结束

这就是我正在使用的：

#include <system_error>
#include <string>

namespace std {

  enum class my_error;

  template <>
  struct is_error_condition_enum<my_error> : public true_type {};
}

namespace my_project {
  enum class my_error {
    warning = 45836431
  };

  namespace internal {
    struct my_error_category : public std::error_category {
      const char* name() const noexcept override {
        return "AAA";
      }
      std::string message(int ev) const noexcept override {
        const std::string message = "BBB";
        return message;
      }
    };
  }
}

inline std::error_code make_error_code(const my_project::my_error &e) {
  return {static_cast<int>(e), my_project::internal::my_error_category()};
};

int main()
{
  std::error_code ec = my_project::my_error::warning;
}

Answer 1

这个有效：

#include <system_error>
#include <string>

namespace my_project {
  enum class my_error {
    warning = 45836431
  };
}

namespace std {
  // you had a typo here, and you defined a different std::my_error class
  template <>
  struct is_error_code_enum<my_project::my_error> : public true_type {};
}

namespace my_project {

  namespace internal {
    struct my_error_category : public std::error_category {
      const char* name() const noexcept override {
        return "AAA";
      }
      std::string message(int ev) const noexcept override {
        const std::string message = "BBB";
        return message;
      }
    };
  }

inline std::error_code make_error_code(const my_project::my_error &e) {
  return {static_cast<int>(e), my_project::internal::my_error_category()};
};
}

int main()
{
  std::error_code ec = my_project::my_error::warning;
}

Clang 的错误消息让我走上了正确的轨道，因为它告诉我为什么它没有使用正确的构造函数。

试图让我的枚举等同于 std::error_code

Trying to make my enum equivalent to std::error_code

c++

c++11

enums

error-code