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問題描述

與所有其他類似問題相反，這個問題是關于使用新的 C++ 特性.

2008 c 有沒有一種簡單的方法可以將 C++ 枚舉轉(zhuǎn)換為字符串?
2008 c 在 C 中使用枚舉類型的變量作為字符串的簡單方法?
2008 c++ 如何輕松地將 C++ 枚舉映射到字符串
2008 c++ 使某些東西既是 C 標識符又是字符串?
2008 c++ 是否有將 C++ 枚舉轉(zhuǎn)換為字符串的簡單腳本?
2009 c++ 如何在 C++ 中使用枚舉作為標志?
2011 c++ 如何將枚舉類型變量轉(zhuǎn)換為字符串?
2011 c++ 枚舉到字符串 C++
2011 c++ 如何將枚舉類型變量轉(zhuǎn)換為字符串?
2012 c 如何在 c 中將枚舉名稱轉(zhuǎn)換為字符串
2013 c 在 C 中對條件編譯的枚舉進行字符串化

看了很多答案，我還沒有找到:

使用 C++11 的優(yōu)雅方式，C++14 或 C++17 新功能
或者在 Boost
其他為 C++20

示例

一個例子往往比一個長的解釋要好.
您可以在 Coliru 上編譯并運行此代碼段.
^{(另一個前面的例子也是可用的)}

#include #include 結構體{枚舉類 MyEnum : char {AAA = -8,BBB = '8',CCC = AAA + BBB};};//用一些更快的編譯時生成的代碼替換magic()//(你可以用 std::string 替換返回類型//如果這對你來說更容易)const char* 魔法 (MyClass::MyEnum e){const std::map我的枚舉字符串{{ MyClass::MyEnum::AAA, "MyClass::MyEnum::AAA";},{ MyClass::MyEnum::BBB, "MyClass::MyEnum::BBB";},{ MyClass::MyEnum::CCC, "MyClass::MyEnum::CCC";}};auto it = MyEnumStrings.find(e);返回它 == MyEnumStrings.end() ?超出范圍":它->第二；}int main(){std::cout <<魔術(MyClass::MyEnum::AAA)<<'
';std::cout <<魔術(MyClass::MyEnum::BBB)<<'
';std::cout <<魔術(MyClass::MyEnum::CCC)<<'
';}

限制條件

請不要重復其他答案或基本鏈接.莉>
請避免基于宏的臃腫答案，或盡量減少 #define 開銷.
請不要手動enum ->string 映射.

很高興有

支持 enum 值從非零的數(shù)字開始
支持負enum值
支持碎片化的enum值
支持類枚舉 (C++11)
支持 class enum : 具有任何允許的 (C++11)
編譯時(非運行時)轉(zhuǎn)換為字符串，
或者至少在運行時快速執(zhí)行(例如 std::map 不是一個好主意......)
constexpr(C++11，然后在 C++14/17/20 中放松)
noexcept (C++11)
C++17/C++20 友好代碼段

一個可能的想法是使用 C++ 編譯器功能在編譯時使用基于 variadic template class 和 constexpr 函數(shù)的元編程技巧生成 C++ 代碼..

解決方案

Magic Enum 僅標頭庫為 C++17 的枚舉(到字符串、從字符串、迭代)提供靜態(tài)反射.

#include 枚舉顏色 { 紅色 = 2, 藍色 = 4, 綠色 = 8 };顏色顏色 = 顏色::紅色；auto color_name = magic_enum::enum_name(color);//顏色名稱 ->紅色的"std::string color_name{"GREEN"};自動顏色 = magic_enum::enum_cast(color_name)如果(顏色.has_value()){//color.value() ->顏色::綠色};

有關更多示例，請查看主存儲庫 https://github.com/Neargye/magic_enum.>

缺點在哪里?

此庫使用特定于編譯器的 hack(基于 __PRETTY_FUNCTION__/__FUNCSIG__)，適用于 Clang >= 5、MSVC >= 15.3 和 GCC >= 9.

枚舉值必須在 [MAGIC_ENUM_RANGE_MIN, MAGIC_ENUM_RANGE_MAX] 范圍內(nèi).

默認MAGIC_ENUM_RANGE_MIN = -128，MAGIC_ENUM_RANGE_MAX = 128.
如果所有枚舉類型默認需要另一個范圍，重新定義宏MAGIC_ENUM_RANGE_MIN和MAGIC_ENUM_RANGE_MAX.
MAGIC_ENUM_RANGE_MIN 必須小于或等于 0，并且必須大于 INT16_MIN.
MAGIC_ENUM_RANGE_MAX 必須大于 0 且必須小于 INT16_MAX.

如果需要特定枚舉類型的另一個范圍，請為必要的枚舉類型添加特殊化 enum_range.

#include 枚舉數(shù) { 一 = 100, 二 = 200, 三 = 300 };命名空間magic_enum {模板 <>struct enum_range{靜態(tài) constexpr int min = 100;靜態(tài) constexpr int 最大值 = 300；};}

Contrary to all other similar questions, this question is about using the new C++ features.

2008 c Is there a simple way to convert C++ enum to string?
2008 c Easy way to use variables of enum types as string in C?
2008 c++ How to easily map c++ enums to strings
2008 c++ Making something both a C identifier and a string?
2008 c++ Is there a simple script to convert C++ enum to string?
2009 c++ How to use enums as flags in C++?
2011 c++ How to convert an enum type variable to a string?
2011 c++ Enum to String C++
2011 c++ How to convert an enum type variable to a string?
2012 c How to convert enum names to string in c
2013 c Stringifying an conditionally compiled enum in C

After reading many answers, I did not yet find any:

Elegant way using C++11, C++14 or C++17 new features
Or something ready-to-use in Boost
Else something planned for C++20

Example

An example is often better than a long explanation.
You can compile and run this snippet on Coliru.
^{(Another former example is also available)}

#include <map>
#include <iostream>

struct MyClass
{
    enum class MyEnum : char {
        AAA = -8,
        BBB = '8',
        CCC = AAA + BBB
    };
};

// Replace magic() by some faster compile-time generated code
// (you're allowed to replace the return type with std::string
// if that's easier for you)
const char* magic (MyClass::MyEnum e)
{
    const std::map<MyClass::MyEnum,const char*> MyEnumStrings {
        { MyClass::MyEnum::AAA, "MyClass::MyEnum::AAA" },
        { MyClass::MyEnum::BBB, "MyClass::MyEnum::BBB" },
        { MyClass::MyEnum::CCC, "MyClass::MyEnum::CCC" }
    };
    auto   it  = MyEnumStrings.find(e);
    return it == MyEnumStrings.end() ? "Out of range" : it->second;
}

int main()
{
   std::cout << magic(MyClass::MyEnum::AAA) <<'
';
   std::cout << magic(MyClass::MyEnum::BBB) <<'
';
   std::cout << magic(MyClass::MyEnum::CCC) <<'
';
}

Constraints

Please no valueless duplication of other answers or basic link.
Please avoid bloat macro-based answer, or try to reduce the #define overhead as minimum as possible.
Please no manual enum -> string mapping.

Nice to have

Support enum values starting from a number different from zero
Support negative enum values
Support fragmented enum values
Support class enum (C++11)
Support class enum : <type> having any allowed <type> (C++11)
Compile-time (not run-time) conversions to a string,
or at least fast execution at run-time (e.g. std::map is not a great idea...)
constexpr (C++11, then relaxed in C++14/17/20)
noexcept (C++11)
C++17/C++20 friendly snippet

One possible idea could be using the C++ compiler capabilities to generate C++ code at compilation-time using meta-programming tricks based on variadic template class and constexpr functions...

解決方案

Magic Enum header-only library provides static reflection for enums (to string, from string, iteration) for C++17.

#include <magic_enum.hpp>

enum Color { RED = 2, BLUE = 4, GREEN = 8 };

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

std::string color_name{"GREEN"};
auto color = magic_enum::enum_cast<Color>(color_name)
if (color.has_value()) {
  // color.value() -> Color::GREEN
};

For more examples check home repository https://github.com/Neargye/magic_enum.

Where is the drawback?

This library uses a compiler-specific hack (based on __PRETTY_FUNCTION__ / __FUNCSIG__), which works on Clang >= 5, MSVC >= 15.3 and GCC >= 9.

Enum value must be in range [MAGIC_ENUM_RANGE_MIN, MAGIC_ENUM_RANGE_MAX].

By default MAGIC_ENUM_RANGE_MIN = -128, MAGIC_ENUM_RANGE_MAX = 128.
If need another range for all enum types by default, redefine the macro MAGIC_ENUM_RANGE_MIN and MAGIC_ENUM_RANGE_MAX.
MAGIC_ENUM_RANGE_MIN must be less or equals than 0 and must be greater than INT16_MIN.
MAGIC_ENUM_RANGE_MAX must be greater than 0 and must be less than INT16_MAX.

If need another range for specific enum type, add specialization enum_range for necessary enum type.

#include <magic_enum.hpp>

enum number { one = 100, two = 200, three = 300 };

namespace magic_enum {
template <>
  struct enum_range<number> {
    static constexpr int min = 100;
    static constexpr int max = 300;
};
}

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在現(xiàn)代 C++11/C++14/C++17 和未來的 C++20 中枚舉到字符