infinite loop ?

[firix]

Hi,
I can not run this program since yesterday.
What I do wrong?

//a.h

#pragma once
#ifndef _A_H_
#define _A_H_

class B;

using namespace std;
class A {
public:
	B *b;
	int i;
	A(int ii);
	A(const A &aa);
	~A();
	void display1()const;
};

#endif

//b.h

#pragma once
#ifndef _B_H_
#define _B_H_


#include <iostream>

using namespace std;

class A;

class B{
public:
	A *a;
	int i;
	B(int ii);
	B(const B &bb);
	~B();
	void display2()const;

};

//a.cpp

#include "a.h"
#include "b.h"

#include <iostream>


using namespace std;

	
	A::A(int ii)
	{
		i = ii;
		b = new B(23);
		cout << "I AM a`S CONSTURCTOR" << endl;
	}
	A::A(const A &aa)
	{
		i = aa.i;
		b = aa.b;
	}

	A::~A()
	{
		delete b;
	}

	void A::display1()const
	{
		cout << i << endl;
		b->display2();
		cout <<"cikti aldim CLASS A"<< endl;
	}

//b.cpp

#include "b.h"
#include "a.h"

#include <iostream>


using namespace std;



	B::B(int ii)
	{
		i = ii;
		a = new A(4);
		cout << "I AM b`S CONSTURCTOR" << endl;
	}

	B::B(const B &bb)
	{
		i = bb.i;
		a = bb.a;
	}

	B::~B()
	{
		delete a;
	}

	
	void B::display2()const
	{
		cout << i << endl;
		a->display1();
		cout <<"cikti aldim CLASS B"<< endl;
	}

//main.cpp

int main()
{
	A a(54);
	B b(23);
	


	a.display1();
	b.display2();
	
	return 0;		
}

[guestgulkan]

Infinite constructor loop by the looks of it.
A creates a B in it's constructor. B creates an A in it's constructor.

So A creates a B which creates an A which creates a B which creates an A which..........


You also have an infinite Display loop.

[firix]

@guestgulkan

I know it already but , I want to do the following;

class A {
public:
	B *b;
	int i;
};

class B{
public:
	A *a;
	int i;
};

class A depends on class B, and class B depends on class A.

Do not have a way of doing this?

[Kyon]

Well, you should use a forward declaration:

class B;

class A {
 ...
};

class B {
 ...
};

[firix]

I have changed, but
now also gives these errors.

error C2011: 'A' : 'class' type redefinition
error C2011: 'B' : 'class' type redefinition

[ne555]

A fatal hug (you can't have 1 to 1)
One of the two constructor should must be changed.

B::B() {
  a = new A( this );
}
A::A(B *_b){
  b = _b;
}

Also check the copy and the destructor

[guestgulkan]

That was what I going to suggest (as in ne555 post): make one of the classes responsible for creating the other but not both like you were doing in the original post.

[firix]

thanks everyone....

[HooklessFastener]

I could easily be wrong, but I think I remember a post stating it's not a good idea to use using namespace std; in a header file. I don't remember why.

[HooklessFastener]

I could easily be wrong, but I think I remember a post stating it's not a good idea to use using namespace std; in a header file. I don't remember why.

[firix]

@HooklessFastener

Why is wrong 'using std namesapace' use?

[ne555]

Because all the files that include that header will be using namespace std.
This could cause conflicts with functions in others namespaces.
(Basically you are killing the reason of use a namespace at all.)

[firix]

How?
I did not understand exactly.

[ne555]

Suppose that you create a class vector (like in maths or physics). That class will support operations like + - * between vector or vector and scalar, and a lot of other methods. Note that vector is a proper name for that class.
To avoid collisions you put that class in the namespace Math.

#include "Math.h"
#include "header_with_using_namespace_std.h"
#include <vector>
//others headers
using Math::vector; //Is going to be used a lot

typedef std::vector<int> array_int; //to avoid confusion

int main(){
//sorry about the names, but that is not important (you could have an array and a math vector in the same source)
  vector<4> rot;
  array_int arr;
  return 0;
}

The compiler yields

reference to 'vector' is ambiguous
candidates are: template<unsigned int n> class Math::vector
/usr/include/c++/4.4/bits/stl_vector.h:170: error:                 template<class _Tp, class _Alloc> class std::vector
'rot' was not declared in this scope

So now I will have to change all the declarations of vector<n> to Math::vector<n>

[firix]

as a result:

it's not a good idea to use using namespace std; in a header file.