VC ++类。 静态变量错误未解决的外部符号

Question

I have this error that keeps haunting me in all of my programs that is probably just me overlooking something.

code snippet where this error appears:

class myClass {
private:
    int x;
public:
    static int getX() {
        x = 10;
        return x;
    }
};

int main() {
    cout << myClass::getX() << endl;
    return 0;
}

The error I am getting says :

error unresolved external symbol

What is causeing this or what is wrong with my code?

Answer 1

A static member function of class foo is not associated with an object of that class (doesn't have the this pointer).

And how can you access the member variables of foo without an object? Unless they are static themselves, you can't.

You must create an instance of foo first.

In your case:

static int myClass::getX() {
    myClass obj;
    obj.x = 10;
    return obj.x;
}

Answer 2

Inside a class you are trying to access the non-static variable using the static method which will not work. You can turn the private member variable x into static and initialize it outside the class. Then your example can look like:

#include <iostream>
class myClass {
private:
    static int x;
public:
    static int getX()
    {
        x = 10;
        return x;
    }
};
int myClass::x = 0;

int main() {
    std::cout << myClass::getX() << std::endl;
    return 0;
}