如何将 Enum 类型的元素插入到 __uint8_t 类型的向量中？答案

【问题标题】：How to insert elements of Enum type into vector of type __uint8_t?如何将 Enum 类型的元素插入到 __uint8_t 类型的向量中？
【发布时间】：2022-11-18 18:27:53
【问题描述】：

我对 C++ 编程很陌生。我想将枚举类型的元素插入到 vector<__uint8_t> 中？即将std::vector <ValType> call的所有元素附加到std::vector<__uint8_t> bravo。有什么办法吗？

  #include <stdio.h>
#include <vector>
#include <cstdint>

enum class ValType : uint8_t
{

    Working = 1,
    Failed = 0,
    Freezed = 0

};

int main()
{
    std::vector<uint8_t> bravo = {23, 23, 23, 22, 5};
    std::vector<ValType> call;
    bravo.insert(bravo.end(), call.begin(), call.end());

    return 0;
}

直播Here

编译时出现错误：

   In file included from c:\program files (x86)\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\include\c++\11.2.0\vector:66,
                 from custom.cpp:2:
c:\program files (x86)\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\include\c++\11.2.0\bits\stl_uninitialized.h: In instantiation of '_ForwardIterator std::uninitialized_copy(_InputIterator, _InputIterator, _ForwardIterator) [with _InputIterator = __gnu_cxx::__normal_iterator<ValType*, std::vector<ValType> >; _ForwardIterator = unsigned char*]':
c:\program files (x86)\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\include\c++\11.2.0\bits\stl_uninitialized.h:333:37:   required from '_ForwardIterator std::__uninitialized_copy_a(_InputIterator, _InputIterator, _ForwardIterator, std::allocator<_Tp>&) [with _InputIterator = __gnu_cxx::__normal_iterator<ValType*, std::vector<ValType> >; _ForwardIterator = unsigned char*; _Tp = unsigned char]'
c:\program files (x86)\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\include\c++\11.2.0\bits\vector.tcc:751:34:   required from 'void std::vector<_Tp, _Alloc>::_M_range_insert(std::vector<_Tp, _Alloc>::iterator, _ForwardIterator, _ForwardIterator, std::forward_iterator_tag) [with _ForwardIterator = __gnu_cxx::__normal_iterator<ValType*, std::vector<ValType> >; _Tp = unsigned char; _Alloc = std::allocator<unsigned char>; std::vector<_Tp, _Alloc>::iterator = std::vector<unsigned char>::iterator]'
c:\program files (x86)\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\include\c++\11.2.0\bits\stl_vector.h:1665:19:   required from 'void std::vector<_Tp, _Alloc>::_M_insert_dispatch(std::vector<_Tp, _Alloc>::iterator, _InputIterator, _InputIterator, std::__false_type) [with _InputIterator = __gnu_cxx::__normal_iterator<ValType*, std::vector<ValType> >; _Tp = unsigned char; _Alloc = std::allocator<unsigned char>; std::vector<_Tp, _Alloc>::iterator = std::vector<unsigned char>::iterator]'
c:\program files (x86)\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\include\c++\11.2.0\bits\stl_vector.h:1383:22:   required from 'std::vector<_Tp, _Alloc>::iterator std::vector<_Tp, _Alloc>::insert(std::vector<_Tp, _Alloc>::const_iterator, _InputIterator, _InputIterator) [with _InputIterator = __gnu_cxx::__normal_iterator<ValType*, std::vector<ValType> >; <template-parameter-2-2> = void; _Tp = unsigned char; _Alloc = std::allocator<unsigned char>; std::vector<_Tp, _Alloc>::iterator = std::vector<unsigned char>::iterator; std::vector<_Tp, _Alloc>::const_iterator = std::vector<unsigned char>::const_iterator]'  
custom.cpp:18:17:   required from here
c:\program files (x86)\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\include\c++\11.2.0\bits\stl_uninitialized.h:138:72: error: static assertion failed: result type must be constructible from value type of input range
  138 |       static_assert(is_constructible<_ValueType2, decltype(*__first)>::value,
      |                                                                        ^~~~~
c:\program files (x86)\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\include\c++\11.2.0\bits\stl_uninitialized.h:138:72: note: 'std::integral_constant<bool, false>::value' evaluates to false
In file included from c:\program files (x86)\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\include\c++\11.2.0\vector:60,
                 from custom.cpp:2:
c:\program files (x86)\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\include\c++\11.2.0\bits\stl_algobase.h: In instantiation of 'static _OI std::__copy_move<false, false, std::random_access_iterator_tag>::__copy_m(_II, _II, _OI) [with _II = ValType*; _OI = unsigned char*]':
c:\program files (x86)\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\include\c++\11.2.0\bits\stl_algobase.h:495:30:   required from '_OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove = false; _II = ValType*; _OI = unsigned char*]'
c:\program files (x86)\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\include\c++\11.2.0\bits\stl_algobase.h:522:42:   required from '_OI std::__copy_move_a1(_II, _II, _OI) [with bool _IsMove = false; _II = ValType*; _OI = unsigned char*]'
c:\program files (x86)\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\include\c++\11.2.0\bits\stl_algobase.h:530:31:   required from '_OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove = false; _II = __gnu_cxx::__normal_iterator<ValType*, std::vector<ValType> >; _OI = __gnu_cxx::__normal_iterator<unsigned char*, std::vector<unsigned char> >]'
c:\program files (x86)\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\include\c++\11.2.0\bits\stl_algobase.h:620:7:   required from '_OI std::copy(_II, _II, _OI) [with _II = __gnu_cxx::__normal_iterator<ValType*, std::vector<ValType> >; _OI = __gnu_cxx::__normal_iterator<unsigned char*, std::vector<unsigned char> >]'
c:\program files (x86)\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\include\c++\11.2.0\bits\vector.tcc:744:16:   required from 'void std::vector<_Tp, _Alloc>::_M_range_insert(std::vector<_Tp, _Alloc>::iterator, _ForwardIterator, _ForwardIterator, std::forward_iterator_tag) [with _ForwardIterator = __gnu_cxx::__normal_iterator<ValType*, std::vector<ValType> >; _Tp = unsigned char; _Alloc = std::allocator<unsigned char>; std::vector<_Tp, _Alloc>::iterator = std::vector<unsigned char>::iterator]'
c:\program files (x86)\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\include\c++\11.2.0\bits\stl_vector.h:1665:19:   required from 'void std::vector<_Tp, _Alloc>::_M_insert_dispatch(std::vector<_Tp, _Alloc>::iterator, _InputIterator, _InputIterator, std::__false_type) [with _InputIterator = __gnu_cxx::__normal_iterator<ValType*, std::vector<ValType> >; _Tp = unsigned char; _Alloc = std::allocator<unsigned char>; std::vector<_Tp, _Alloc>::iterator = std::vector<unsigned char>::iterator]'
c:\program files (x86)\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\include\c++\11.2.0\bits\stl_vector.h:1383:22:   required from 'std::vector<_Tp, _Alloc>::iterator std::vector<_Tp, _Alloc>::insert(std::vector<_Tp, _Alloc>::const_iterator, _InputIterator, _InputIterator) [with _InputIterator = __gnu_cxx::__normal_iterator<ValType*, std::vector<ValType> >; <template-parameter-2-2> = void; _Tp = unsigned char; _Alloc = std::allocator<unsigned char>; std::vector<_Tp, _Alloc>::iterator = std::vector<unsigned char>::iterator; std::vector<_Tp, _Alloc>::const_iterator = std::vector<unsigned char>::const_iterator]'  
custom.cpp:18:17:   required from here
c:\program files (x86)\mingw-w64\i686-8.1.0-posix-dwarf-rt_v6-rev0\mingw32\include\c++\11.2.0\bits\stl_algobase.h:385:25: error: cannot convert 'ValType' to 'unsigned char' in assignment
  385 |               *__result = *__first;
      |               ~~~~~~~~~~^~~~~~~~~~

有人可以告诉我这样做的正确方法吗？

【问题讨论】：

在一个不相关的问题上，你为什么使用非标准和不可移植的__uint8_t而不是标准的uint8_t？
@Someprogrammerdude ..抱歉，在线的是 ___ uint8_t 而不是 uint8_t..所以我放一样的。你可以假设 uint8_t
包括定义标准整数类型的 <cstdint>。
@Someprogrammerdude 添加了 <cstdint>。谢谢
这回答了你的问题了吗？ Can an enum class be converted to the underlying type?

标签： c++ c++11 vector enums c++17

【解决方案1】：

这在例如中解释。 this scope enumeration reference:

没有从作用域枚举器的值到整数类型的隐式转换, 尽管 static_cast 可用于获取枚举器的数值。

_{[强调我的]}

因此，虽然在定义枚举时它可能看起来像继承，但事实并非如此。 ValType 类型是一种完全独立的类型，不能与任何其他纯整数类型相互转换，即使是用作枚举基类型的类型。

这意味着您不能简单地将 ValType 元素向量复制到 uint8_t 元素向量。如果你需要做这样的复制，你必须实现你自己的转换（使用例如static_cast），也许使用std::transform和back insert iterator。

【讨论】：

谢谢.. If you need to do such a copy you must implement your own conversion (using e.g. static_cast), perhaps using std::transform and an back insert iterator. 你能告诉我如何解决我的问题吗？