Pointer by reference problem

[dragonklavier]

Hello.

I have problems with pointers by reference topic. This is the isue:

I have:

- One class "A" with a class "B" and "C" instanced inside.
- A class D. This constains a set of Strings. And it is declared as a data member in "A" ,"B" and "C".


The problem is that I have to modify the "D" values (I have an instance of D class in A ,B and C) in any of the three classes and I need to manage a same value.

So, I think:

Class A.
{
   B * m_b;
   C * m_c;
   D * m_d;

   
   A()
   {
   m_b= new B(&m_d);
   m_c= new C(&m_d);
   }
}

Class B.
{
  D* m_d;
  
  B(D* &d)
  {
  m_d=d
  }
}



Class C.
{
  D* m_d;
  
  C(D* &d)
  {
  m_d=d
  }
}

My problem is that before y create m_d in B, I cant see the address in m_d of C.

Plese...I need your help

Thanks a lot!

[laserlight]

My problem is that before y create m_d in B, I cant see the address in m_d of C.

I don't see how that is a problem: both m_d pointers in the B and C objects point to the same D object. Your problem is that you did not create this D object, and then you made a type mistake, i.e., &m_d is a D**, but you wanted to pass a D* to the constructors of B and C. Personally, I don't need why you need dynamic memory allocation here, so if I were you, I would go for something like:

class D
{
    // ...
};

class B
{
public:
    B(D* d) : m_d(d) {}
private:
    D* m_d;
};

class C
{
public:
    C(D* d) : m_d(d) {}
private:
    D* m_d;
};

class A
{
public:
    A() : m_d(/* whatever */), m_b(&m_d), m_c(&m_d) {}
private:
    D m_d;
    B m_b;
    C m_c;
};

I took care to declare m_d first in A in case the constructors of B and C should want to do something with the D object.