2

我正在尝试使用枚举类和 std::string 的 std::map,但我遇到了一些错误。我正在使用带有 -std=c++0x 的 gcc 4.4.7(这是固定的)

在 .h 文件中:

enum class state_t{
    unknown,
    off,
    on,
    fault
};

typedef std::map<state_t,std::string> statemap_t;

在 .cpp 文件中:

statemap_t state={
   {state_t::unknown,"unknown"}
   {state_t::off,"off"}
   {state_t::on,"on"}
   {state_t::fault,"fault"}
}

允许状态转换的方法如下:

Foo::allowStateChange(const state_t localState, const state_t globalState, const state_t newState){
    //Some code to verify if the state transition is allowed.
    std::cout << "Device Local State:" << state.find(localState)->second << "Device Global State:" << state.find(globalState)->second << "Device New State:" << state.find(newState)->second << std::endl;
}

编译时,我得到下一个错误:错误:'state_t'和'state_t'类型的无效操作数到二进制'operator<'

如果我将其更改enum class state_tenum state_t它可以工作。有没有办法在地图中找到枚举类?

提前致谢。

4

2 回答 2

2

我假设您使用的 GCC 编译器版本不支持与枚举类相关的所有基础结构。因此,您需要自己实现缺少的运算符,如下所示:

inline bool operator <(const state_t left, const state_t right)
{
    return static_cast<int>(left) < static_cast<int>(right);
}

inline bool operator >(const state_t left, const state_t right)
{
    return static_cast<int>(left) > static_cast<int>(right);
}

在 C++11 中,这些函数可能是通过模板特化实现的,使用 std::underlying_type 作为 static_cast 和将它们专门绑定到枚举类的限定符,其中一些可能在 -std=c++0x 下不可用编译器版本

于 2018-10-22T11:53:39.447 回答
2

以下代码可以正常工作(在 Visual Studio 2015 (v140) 上;在您的情况下使用哪个编译器?):

#include <string>
#include <iostream>
#include <map>

using namespace std;

enum class state_t {
    unknown,
    off,
    on,
    fault
};

typedef std::map<state_t, std::string> statemap_t;

statemap_t state = {
    { state_t::unknown,"unknown" },
    { state_t::off,"off"},
    { state_t::on,"on"},
    { state_t::fault,"fault"}
};

void allowStateChange(const state_t localState, const state_t globalState,     const state_t newState) {
    //Some code to verify if the state transition is allowed.
    std::cout 
        << "Device Local State:" 
        << state.find(localState)->second 
        << ", Device Global State:" 
        << state.find(globalState)->second 
        << ", Device New State:" 
        << state.find(newState)->second 
        << std::endl;
}

int main()
{
    allowStateChange(state_t::on, state_t::off, state_t::fault);
    return 0;
}

BWT,state_t 中有一个拼写错误“unkmown”。

于 2017-02-24T11:27:56.807 回答