Magic Enum C++

Header-only C++17 library provides static reflection for enums, work with any enum type without any macro or boilerplate code.

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Documentation

• Reference
• Limitations
• Integration

Features & Examples

• Basic

  #include <magic_enum/magic_enum.hpp>
  #include <iostream>
  
  enum class Color : { RED = -10, BLUE = 0, GREEN = 10 };
  
  int main() {
    Color c1 = Color::RED;
    std::cout << magic_enum::enum_name(c1) << std::endl; // RED
    return 0;
  }

• Enum value to string

  Color color = Color::RED;
  auto color_name = magic_enum::enum_name(color);
  // color_name -> "RED"

• String to enum value

  std::string color_name{"GREEN"};
  auto color = magic_enum::enum_cast<Color>(color_name);
  if (color.has_value()) {
    // color.value() -> Color::GREEN
  }
  
  // case insensitive enum_cast
  auto color = magic_enum::enum_cast<Color>(value, magic_enum::case_insensitive);
  
  // enum_cast with BinaryPredicate
  auto color = magic_enum::enum_cast<Color>(value, [](char lhs, char rhs) { return std::tolower(lhs) == std::tolower(rhs); }
  
  // enum_cast with default
  auto color_or_default = magic_enum::enum_cast<Color>(value).value_or(Color::NONE);

• Integer to enum value

  int color_integer = 2;
  auto color = magic_enum::enum_cast<Color>(color_integer);
  if (color.has_value()) {
    // color.value() -> Color::BLUE
  }
  
  auto color_or_default = magic_enum::enum_cast<Color>(value).value_or(Color::NONE);

• Indexed access to enum value

  std::size_t i = 0;
  Color color = magic_enum::enum_value<Color>(i);
  // color -> Color::RED

• Enum value sequence

  constexpr auto colors = magic_enum::enum_values<Color>();
  // colors -> {Color::RED, Color::BLUE, Color::GREEN}
  // colors[0] -> Color::RED

• Number of enum elements

  constexpr std::size_t color_count = magic_enum::enum_count<Color>();
  // color_count -> 3

• Enum value to integer

  Color color = Color::RED;
  auto color_integer = magic_enum::enum_integer(color); // or magic_enum::enum_underlying(color);
  // color_integer -> 1

• Enum names sequence

  constexpr auto color_names = magic_enum::enum_names<Color>();
  // color_names -> {"RED", "BLUE", "GREEN"}
  // color_names[0] -> "RED"

• Enum entries sequence

  constexpr auto color_entries = magic_enum::enum_entries<Color>();
  // color_entries -> {{Color::RED, "RED"}, {Color::BLUE, "BLUE"}, {Color::GREEN, "GREEN"}}
  // color_entries[0].first -> Color::RED
  // color_entries[0].second -> "RED"

• Enum fusion for multi-level switch/case statements

  switch (magic_enum::enum_fuse(color, direction).value()) {
    case magic_enum::enum_fuse(Color::RED, Directions::Up).value(): // ...
    case magic_enum::enum_fuse(Color::BLUE, Directions::Down).value(): // ...
  // ...
  }

• Enum switch runtime value as constexpr constant

  Color color = Color::RED;
  magic_enum::enum_switch([] (auto val) {
    constexpr Color c_color = val;
    // ...
  }, color);

• Enum iterate for each enum as constexpr constant

  magic_enum::enum_for_each<Color>([] (auto val) {
    constexpr Color c_color = val;
    // ...
  });

• Check if enum contains

  magic_enum::enum_contains(Color::GREEN); // -> true
  magic_enum::enum_contains<Color>(2); // -> true
  magic_enum::enum_contains<Color>(123); // -> false
  magic_enum::enum_contains<Color>("GREEN"); // -> true
  magic_enum::enum_contains<Color>("fda"); // -> false

• Enum index in sequence

  constexpr auto color_index = magic_enum::enum_index(Color::BLUE);
  // color_index.value() -> 1
  // color_index.has_value() -> true

• Functions for flags

  enum Directions : std::uint64_t {
    Left = 1,
    Down = 2,
    Up = 4,
    Right = 8,
  };
  template <>
  struct magic_enum::customize::enum_range<Directions> {
    static constexpr bool is_flags = true;
  };
  
  magic_enum::enum_flags_name(Directions::Up | Directions::Right); // -> "Directions::Up|Directions::Right"
  magic_enum::enum_flags_contains(Directions::Up | Directions::Right); // -> true
  magic_enum::enum_flags_cast(3); // -> "Directions::Left|Directions::Down"

• Enum type name

  Color color = Color::RED;
  auto type_name = magic_enum::enum_type_name<decltype(color)>();
  // type_name -> "Color"

• IOstream operator for enum

  using magic_enum::iostream_operators::operator<<; // out-of-the-box ostream operators for enums.
  Color color = Color::BLUE;
  std::cout << color << std::endl; // "BLUE"

  using magic_enum::iostream_operators::operator>>; // out-of-the-box istream operators for enums.
  Color color;
  std::cin >> color;

• Bitwise operator for enum

  enum class Flags { A = 1 << 0, B = 1 << 1, C = 1 << 2, D = 1 << 3 };
  using namespace magic_enum::bitwise_operators; // out-of-the-box bitwise operators for enums.
  // Support operators: ~, |, &, ^, |=, &=, ^=.
  Flags flags = Flags::A | Flags::B & ~Flags::C;

• Checks whether type is an Unscoped enumeration.

  enum color { red, green, blue };
  enum class direction { left, right };
  
  magic_enum::is_unscoped_enum<color>::value -> true
  magic_enum::is_unscoped_enum<direction>::value -> false
  magic_enum::is_unscoped_enum<int>::value -> false
  
  // Helper variable template.
  magic_enum::is_unscoped_enum_v<color> -> true

• Checks whether type is an Scoped enumeration.

  enum color { red, green, blue };
  enum class direction { left, right };
  
  magic_enum::is_scoped_enum<color>::value -> false
  magic_enum::is_scoped_enum<direction>::value -> true
  magic_enum::is_scoped_enum<int>::value -> false
  
  // Helper variable template.
  magic_enum::is_scoped_enum_v<direction> -> true

• Static storage enum variable to string This version is much lighter on the compile times and is not restricted to the enum_range limitation.

  constexpr Color color = Color::BLUE;
  constexpr auto color_name = magic_enum::enum_name<color>();
  // color_name -> "BLUE"

• containers::array array container for enums.

  magic_enum::containers::array<Color, RGB> color_rgb_array {};
  color_rgb_array[Color::RED] = {255, 0, 0};
  color_rgb_array[Color::GREEN] = {0, 255, 0};
  color_rgb_array[Color::BLUE] = {0, 0, 255};
  magic_enum::containers::get<Color::BLUE>(color_rgb_array) // -> RGB{0, 0, 255}

• containers::bitset bitset container for enums.

  constexpr magic_enum::containers::bitset<Color> color_bitset_red_green {Color::RED|Color::GREEN};
  bool all = color_bitset_red_green.all();
  // all -> false
  // Color::BLUE is missing
  bool test = color_bitset_red_green.test(Color::RED);
  // test -> true

• containers::set set container for enums.

  auto color_set = magic_enum::containers::set<Color>();
  bool empty = color_set.empty();
  // empty -> true
  color_set.insert(Color::GREEN);
  color_set.insert(Color::BLUE);
  color_set.insert(Color::RED);
  std::size_t size = color_set.size();
  // size -> 3

• Improved UB-free "SFINAE-friendly" underlying_type.

  magic_enum::underlying_type<color>::type -> int
  
  // Helper types.
  magic_enum::underlying_type_t<Direction> -> int

Remarks

• magic_enum does not pretend to be a silver bullet for reflection for enums, it was originally designed for small enum.

• Before use, read the limitations of functionality.

Integration

• You should add the required file magic_enum.hpp, and optionally other headers from include dir or release archive. Alternatively, you can build the library with CMake.

• If you are using vcpkg on your project for external dependencies, then you can use the magic-enum package.

• If you are using Conan to manage your dependencies, merely add magic_enum/x.y.z to your conan's requires, where x.y.z is the release version you want to use.

• If you are using Build2 to build and manage your dependencies, add depends: magic_enum ^x.y.z to the manifest file where x.y.z is the release version you want to use. You can then import the target using magic_enum%lib{magic_enum}.

• Alternatively, you can use something like CPM which is based on CMake's Fetch_Content module.

  CPMAddPackage(
      NAME magic_enum
      GITHUB_REPOSITORY Neargye/magic_enum
      GIT_TAG x.y.z # Where `x.y.z` is the release version you want to use.
  )

• Bazel is also supported, simply add to your WORKSPACE file:

  http_archive(
      name = "magic_enum",
      strip_prefix = "magic_enum-<commit>",
      urls = ["https://github.com/Neargye/magic_enum/archive/<commit>.zip"],
  )
  

  To use bazel inside the repository it's possible to do:

  bazel build //...
  bazel test //...
  bazel run //example
  

  (Note that you must use a supported compiler or specify it with export CC= <compiler>.)

• If you are using Ros, you can include this package by adding <depend>magic_enum</depend> to your package.xml and include this package in your workspace. In your CMakeLists.txt add the following:

  find_package(magic_enum CONFIG REQUIRED)
  ...
  target_link_libraries(your_executable magic_enum::magic_enum)

Compiler compatibility

• Clang/LLVM >= 5
• MSVC++ >= 14.11 / Visual Studio >= 2017
• Xcode >= 10
• GCC >= 9
• MinGW >= 9

Licensed under the MIT License