c++ access private static member from implementation file

Question

I have a header file like so

#ifndef MYAPP
#define MYAPP
#include <map>
namespace MyApp{
    class MyClass{
        private:
            static std::map<int, bool> SomeMap;
        public:
            static void DoSomething(int arg);
    };
}
#endif MYAPP

and an implemtation file

#include "Header.h"
#include <map>
namespace MyApp{
    void MyClass::DoSomething(int arg){
        if(MyClass::SomeMap[5]){
            ...
        }
    }
}

When I tried to compile it, it gives me an error class "MyClass" has no member "SomeMap". How can I fix this?

Possible duplicate of [Undefined reference to static class member](https://stackoverflow.com/questions/272900/undefined-reference-to-static-class-member) — user4581301, Dec 15 '17 at 06:07

score 1 · Accepted Answer · answered Dec 15 '17 at 06:11

You have forgotten to define your static variable:

#include "Header.h"
#include <map>
namespace MyApp{
    std::map<int, bool> MyClass::SomeMap;

    void MyClass::DoSomething(int arg){
        if(MyClass::SomeMap[5]){
            ...
        }
    }
}

P.S. Your example code is missing ; after class definition.

c++ access private static member from implementation file

1 Answers1