Question

How to use static variable in class with C++

Answer 1

#include <iostream>

class Example {
    public:
        static int num;
        Example() {};
};
    
int Example::num = 23;

int main() {
    Example obj;
    
    std::cout << obj.num << "\n";
    
    int x = obj.num + 47;
    std::cout << x;
}
  
  
  
  
/*
run:
  
23
70
  
*/

 

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Answer 2

#include <iostream>
#include <cmath>

class Circle {
public:
    double r;
    static double pi; // static variable - one copy for all objects
    static double newArea(double r) { return M_PI * r * r; }
};

int main()
{
    double area = Circle::newArea(3);
    
    std::cout << area;
}



/*
run:

28.2743

*/

 

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