object oriented programming,use of static function to count objects

Question

I want to display the objects of the class and the number of objects by using a static function. I typed this code but it does not work. It gives an error Too many types indeclaration" and "undefined symbol getCount. Can anyone help me? where is actually error in this code?

#include<iostream>
#include<string>

class Bag {
private:
    static int objectCount;
    int Weight;
    std::string Brand;
    std::string Type;
    std::string Material;
    std::string Colour;
public:
    Bag(int W, std::string B, std::string T, std::string M, std::string C) {
        Weight = W;
        Brand = B;
        Type = T;
        Material = M;
        Colour = C;
        objectCount++;
    }

    void print() {
        std::cout << "\n";
        std::cout << "Bag: \n\n";
        std::cout << "Weight:\t\t" << Weight   << "kg" << '\n';
        std::cout << "Brand:\t\t"  << Brand    << '\n' << "Type:\t\t"   << Type   << '\n';
        std::cout << "Material:\t" << Material << '\n' << "colour:\t\t" << Colour << std::endl;
    }

    static int getCount() {
        return objectCount;
    }
};

int Bag::objectCount = 0;

int main() {
    Bag bag_1(2, "Slazanger", "Atheletic Bag", "Polyethylene", "Brown");
    bag_1.print();
    std::cout << "object count " << Bag::getCount() << '\n';

    Bag bag_2(4, "Samsonite", "Travel Bag", "Synthetic Fibre", "Gray");
    bag_2.print();
    std::cout << "object count " << Bag::getCount() << '\n';

    Bag bag_3(5, "Herschel", "Duffel bag", "Leather", "Black");
    bag_3.print();
    std::cout << "object count " << Bag::getCount() << '\n';

    Bag bag_4(3, "Kewin Woods", "Hand Bag", "Fibre", "Blue");
    bag_4.print();
    std::cout << "object count " << Bag::getCount() << std::endl;

    while(!std::cin.get());
    return 0;
}

Answer 1

You are scoping it incorrectly, getCount is statically scoped to the translation unit, not the class. Thus it has no symbol named objectCount available to it.

To fix it, merely put the method inside the class.

class Bag {
private:
    static int objectCount;
    int Weight;
    string Brand,Type,Material,Colour;
public:
    Bag(int W ,string B ,string T,string M,string C)
    {
        Weight=W;
        Brand=B;
        Type=T;
        Material=M;
        Colour=C;

        objectCount++;
    }

    void print()
    {
        cout<<"\n";
        cout<<"Bag: \n\n";
        cout<<"Weight:\t\t"<<Weight<<"kg"<<endl;
        cout<<"Brand:\t\t"<<Brand<<endl<<"Type:\t\t"<<Type<<endl;
        cout<<"Material:\t"<<Material<<endl<<"colour:\t\t"<<Colour<<endl;
    }

   static int getCount()
   {
       cout<< objectCount;
   }
};

Aditionally, Borland is a really old compiler and suprised to even still hear it's name, last release was around 15 years ago so you should really consider using clang, gcc or msvc and upgrading your learning materials to something less ancient. There has been alot of evolution in terms of practices, standards and compiler conformance.

For example, C++ headers don't have an extension, and other small things like that.

Answer 2

This is a working version of your code:

#include <iostream>
#include <cstring>

using namespace std;

class Bag {
private:
  static int objectCount;
  int Weight;
  string Brand, Type, Material, Colour;

public:
  Bag(int W, string B, string T, string M, string C) //constructor
  {
    Weight = W;
    Brand = B;
    Type = T;
    Material = M;
    Colour = C;

    objectCount++;
  }
  void print() {
    cout << "\n";
    cout << "Bag: \n\n";
    cout << "Weight:\t\t" << Weight << "kg" << endl;
    cout << "Brand:\t\t" << Brand << endl << "Type:\t\t" << Type << endl;
    cout << "Material:\t" << Material << endl << "colour:\t\t" << Colour
         << endl;
  }
  static int getCount() //static function to count objects
  {
    cout << objectCount;
  };
};


int Bag::objectCount = 0;
int main() {

  Bag bag_1(2, "Slazanger", "Atheletic Bag", "Polyethylene", "Brown");

  Bag bag_2(4, "Samsonite", "Travel Bag", "Synthetic Fibre", "Gray");
  Bag bag_3(5, "Herschel", "Duffel bag", "Leather", "Black");
  Bag bag_4(3, "Kewin Woods", "Hand Bag", "Fibre", "Blue");
  bag_1.print();
  cout << "object count" << Bag::getCount();
  bag_2.print();
  cout << "object count" << Bag::getCount();

  bag_3.print();
  cout << "object count" << Bag::getCount();

  bag_4.print();
  cout << "object count" << Bag::getCount();
}

There were several mistakes in the version you posted:

• in C++ you don't need the .h when including files
• you were using cout without the std:: qualifier or adding using namespace std; to your source. Also, please read this.
• your static function was not declared/defined inside your class definition
• it should be int main instead of void main

One last note: I removed your #include <conio.h> which should probably read #include <conio> and getch because I compiled this on a linux machine. Feel free to add them back in if you want them.