Can't access static member function C++

Question

I have a static member of a class of type map. but whenever I try to access it I always get an error. For example

// a.h
class a {
    public:
        static map<string, int>m;
    a() {
    }
    ~a() {
    }
};

// a.cpp
    a::m['ADD']=1;

this is the error I get = "Size of array has non-integer type 'const char[4]" I also get a weird error in the linker.

Answer 1

You need to define the map before you can use it:

std::map<std::string, int> a::m = std::map<std::string, int>{{"ADD", 1}};

This will initialize it to a map holding one element with key std::string("ADD") and value 1 .

Note also, use double quotes for string literals.

Answer 2

Compiler error: You are using single-quotes when you probably meant to use double quotes.

Linker error: When defining static variables of a class, you also have to define them in a cpp file somewhere. Add the following line to your cpp file:

map<string, int> a::m;