如何在C++中初始化属于全局范围的静态成员

Question

In my project, there are two classes named Configuration. One is in the namespace common. The other has no namespace, so it's in global scope.The class in global scope is like this: Configuration.h:

class Configuration
{
    public:
        static int a;
        static string b;
        void func();
}

Configuration.cpp:

#include "Configuration.h"
int ::Configuration a; //ok
std::string ::Configuration b;//error,the complier treat it like this "std::string::Configuration"

The message from complier is like this: configuration.cpp:17: error: 'std::string::Configuration' has not been declared

How to solve this problem, and why the complier treat "std::string ::Configuration" as "std::string::Configuration"?

Answer 1

You don't need to use the global scope explicitly here, you can just omit the :: .

int Configuration::a;
std::string Configuration::b;

If you really want to, you need to create one extra level of indirection somehow:

typedef ::Configuration conf;
std::string conf::b;