CODEWITHSUNDEEP
c++classstatic
JayY
JayY

Reputation: 167

C++: static variables not changing with static set() function

After reading StackOverflow's discussions and implementing some advices, I have these pieces of code intended just to test the behavior of static members of a class. Here is the header, which has the class declaration:

class OurClass
    {
    private:
        static int x, y;

    public:
        static void setVals(int valx, int valy);
        static int getValx();
        static int getValy();
        static void initialize();
    };

And here is the cpp file, which has the definition of these members as well as the main() function:

#include <iostream>
#include "OurClass.hpp"

using namespace std;

void OurClass::initialize()
    {
    static int x = 0;
    static int y = 0;
    }

void OurClass::setVals(int valx, int valy)
    {
    static int x = valx;
    static int y = valy;
    }

int OurClass::getValx()
    {
    static int x;
    return x;
    }

int OurClass::getValy()
    {
    static int y;
    return y;
    }


int main(void)
{
OurClass::inicializa();

cout << "Provide x and y..." << endl;

OurClass::setVals(cin.get(), cin.get());

cout << "Value of x: " << OurClass::getValx() << endl;
cout << "Value of y: " << OurClass::getValy() << endl;
return 0;
}

So, assuming that a static variable exists for the class, and that static functions only access static variables, I was expecting that x and y would have the values that we read from the keyboard with the setVals() call in main(). But when printing their values in the couts, they still have the value we assigned in the initialize() function (which BTW was another suggestion I got here, that is, initialize a static variable in a method). I am also unable to refer directly to the variables by OurClass::x or y even if I make them public. Do you guys know why?

Upvotes: 0

Views: 2441

Answers (2)

Sachith Dickwella
Sachith Dickwella

Reputation: 1490

First you need to access your local class's static variable instead declaring new method local variables in each method. Check below.

class Out {
private:
    static int x, y;

public:
    void set(int x, int y);
    int getSum();
};

int Out::x = 0;
int Out::y = 0;

void Out::set(int x, int y) {
    Out::x = x;
    Out::y = y;
}

int Out::getSum() {
    return Out::x + Out::y;
}

Upvotes: 1

Maxim Egorushkin
Maxim Egorushkin

Reputation: 136306

Instead of setting values of existing variables this code creates new local static variables. Fix:

void OurClass::initialize()
{
    x = 0;
    y = 0;
}

void OurClass::setVals(int valx, int valy)
{
    x = valx;
    y = valy;
}

int OurClass::getValx()
{
    return x;
}

int OurClass::getValy()
{
    return y;
}

And add the definitions of those static variables in a .cc file (not header):

int OurClass::x;
int OurClass::y;

Upvotes: 1

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