"Storage class specified" for C++ code

[greenlife55]

Hi all

I am running an image processing algorithm using OpenCV library and C++ in Eclipse SDE. here is my code...the unnecessary stuff is removed..

#include <iostream>
#include <fstream>
#include <stdio.h>
#include "evalulation_criteria.h"

using namespace std;

int main( int argc, char** argv )
{

        evaluation_criteria e_criteria
        ofstream save_inv;
	save_inv.open("saved_data_invariant.txt");

        while(.....) {       //OpenCV structures follow
        
        //call to member function of class e_criteria

        }
        save_inv.close();
}

//class header

#ifndef EVALUTATION_CRITERIA_H_
#define EVALUTATION_CRITERIA_H_


#include "opencv/cxcore.h"
#include "opencv/cv.h"
#include <fstream>

using namespace std;

class evalutation_criteria {

private:

extern ofstream save_inv;
// other member data

public:

//member data


};

#endif  /* EVALUTATION_CRITERIA_H_ */


//class implementation 


#include <iostream>
#include "opencv/cv.h"
#include "opencv/highgui.h"
#include "opencv/cxcore.h"

#include "evalutation_criteria.h"

using namespace std;

// void constructor and destructor

void evalutation_criteria::calc(....){

        save_inv<<(float) value;  

}

I get only the "storage class specified for save_inv" error. I have checked the program many times for any missing semicolons but it compiles fine if i remove the extern keyboard (which is clearly not the purpose)....How do I pass the ofstream objects between main and class member functions to write to the same txt file then?

Thanks for all your help

[writetonsharma]

do you want to use a typedef?

[greenlife55]

I dont mind using typedef but i do not know how it will solve my problem..i am a newbie to c++ so kindly bear with me.

[coder777]

This extern ofstream save_inv; doesn't work. You cannot make a local variable extern. Pass ofstream &save_inv to evalutation_criteria::calc()

[greenlife55]

thanks coder777 for that serious error. i cant send the

ofstream &save_inv

to the function as it hampers my requirements. I tried creating save_inv as a global object but the error still lingers. I know global variables are not a good programming practice, but since I am developing an algorithm solely it should be fine I guess.

[greenlife55]

thanks coder777 I have solved it with what you said. I passed the address! I am a big fan of pointers now :D