C++ class with static pointer

Question

I don't understand pointers and references very well yet, but I have a class with static methods and variables that will be referenced from main and other classes. I have a variable defined in main() that I want to pass to a variable in this class with static functions. I want those functions to change the value of the variable that is seen in the main() scope.

This is an example of what I am trying to do, but I get compiler errors...

class foo
{
    public:

    static int *myPtr;

    bool somfunction() {
        *myPtr = 1;
        return true;
    }
};

int main()
{
    int flag = 0;
    foo::myPtr = &flag;

    return 0;
}

Answer 1

Provide the definition of the static variable outside the class as:

//foo.h
class foo
{
    public:

    static int *myPtr; //its just a declaration, not a definition!

    bool somfunction() {
        *myPtr = 1;
        //where is return statement?
    }
};  //<------------- you also forgot the semicolon


/////////////////////////////////////////////////////////////////
//foo.cpp
#include "foo.h"  //must include this!

int *foo::myPtr; //its a definition

Beside that, you also forgot the semicolon as indicated in the comment above, and somefunction needs to return a bool value.

Answer 2

#include <iostream>
using namespace std;

class foo
{
public:

static int *myPtr;

bool somfunction() {
    *myPtr = 1;
    return true;
}
};
//////////////////////////////////////////////////
int* foo::myPtr=new int(5);     //You forgot to initialize a static data member  
//////////////////////////////////////////////////
int main()
{
int flag = 0;
foo::myPtr = &flag;
return 0;
}