如何使用std :: map <enum class，std :: string>？

Question

我想std :: map，一个枚举类和一个std :: string，但我得到一些错误。 我使用gcc 4.4.7与-std =的C++ 0x（这是固定的）

在h文件：

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

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

在cpp文件：

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

的法允许的状态transitionis，如：

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; 
} 

compilling时，我得到一个错误： 错误：我类型“state_t”和“state_t”二进制“操作<”

的NVALID操作数如果我改变enum class state_t到enum state_t它的工作原理。 有没有什么方法可以在地图上找到一个枚举类？

在此先感谢。

Answer 1

下面的代码工作得很好（在Visual Studio的2015年（V140）;其编译器在你的情况下使用？）：

#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，有在state_t一个拼错 “unkmown”。