c++ static class?

Question

This program won't compile correctly

// Bell.h file
#ifndef BELL_H
#define BELL_H

class Bell
{
private:
	int count1;
	static int count2;
public:
	Bell()
	{	count1 = 0;	}
	void ring(int);
	int getCount() const
	{	return count1;	}
	static int getStaticCount() const
	{	return count2;	}
};

#endif

//specification of ring function and main function (Bell.cpp)
#include <iostream>
#include "Bell.h"
using namespace std;

void Bell::ring(int num_rings)
{	
	for (int index = 0; index < num_rings; index++)
	{
		cout << "ring ";
		count1++;
		count2++;
	}
}

int main()
{
	const int NUM_RINGS1 = 3, NUM_RINGS2 = 4;
	Bell bell1, bell2;
	bell1.ring(NUM_RINGS1);
	bell2.ring(NUM_RINGS2);
	cout << "Count for first bell: " << bell1.getCount();
	cout << "Count for second bell: " << bell2.getCount();
	cout << "Static Counter: " << bell1.getStaticCount();
	system("pause");
	return 0;
}

Basically bell1 should ring 3 times and bell2 should ring 4 times
and should print out the count for each bell and the static counter,
which is the same for both.

Please help me? I'm not so good with programming

husoski · Accepted Answer

Take the const off of the declaration for getStaticCount. That only applies to non-static member functions. (see below)

Add a *definition* (the class only declares it) in a .cpp file. Put it next to (but NOT inside of) the Bell::ring() method definition (before main()) for now, but both of those would ordinarily be in Bell.cpp as the implementation of the class.

int Bell::count2 = 0; // static ring counter

There is no "constructor" for the class to initialize static member variables, so you have to do that in a file-level declaration, like that one.

After that, you'll get:

ring ring ring ring ring ring ring Count for first bell: 3Count for second bell: 4Static Counter: 7

...so it looks like you need to add << endl; to some of your cout<< lines.

About const member functions: The "const" in a member function makes the object the function is called on a constant. Since a static member function isn't associated with any object, there is no reason for const.

PS: You should also add "#include <cstdlib>" if you use system(), since that's where system() is officially defined. VC++ includes this as part of <iostream>, but that's not required (or prohibited, apparently) so other compilers for Windows may fail. MinGW is one of them. I just commented out the system() call to get this to compile under Code::Blocks with MinGW. (C::B automatically inserts a pause at end of run, anyway.)

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c++ static class?

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