class contains its self pointer

Hi
i want to ask is it normal when I intended to design a class Hierarchy like following?

Code:

---

class Base {
...
};

class Manager: public Base {
...
  void init() { _p = new Derived(); }
private:
  Base *_p;

};

class Derived: public Base {
...
};

---

I am at a situation that I think the only solution is have a reference to DerivedB object in DerivedA.

Just in case someone will curious about how this occurs.
Actually I am using a third party source code. And he defines an entry point which I need to pass a parameter in Base*... Normally, simply derive from Base, and pass the instance to it will be fine. However, I am trying to design a flexible codes, and I want to create a manager class (which I define as above). And make original user defined class in its data member.
However, I think if I design this way, it looks just so unreadable for the maintainer.
I need advice.
Really appreciate for comments. Thx

Why is Manager derived from Base?

Quote:

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Originally Posted by laserlight

Why is Manager derived from Base?

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Manager class derived from the Base is because that third party package defines a entry point
in main.cpp

Something like

Code:

---

in Main.cpp
  RunApp(MyObj());

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However, the RunApp needs to pass a Base*. Therefore I have no choice everything I need to pass a reference in the Base class Hierarchy.
My intention to create Manager class is I try to use Manage class as Contexts in design patters of State Pattern. Thus the state reference(which is DerivedB as I mentioned) can
change dynamically. But DerivedB needs some parameter in Base class. So it derive from Base class, too.

Well you manager class doesn't need to inherit from the base class it only needs an object of type Base*. you would do something like

Code:

---

class Manager
{
public:
    Manager(Base*);    // simply constructor
    void SetObject(Base*);  // deletes data and then sets this one.
    Base* GetObject() const;  // returns data
private:
    Base* data;
};

// later on in your code
Base * base;
Manager manager(base);
RunApp(manager.GetObject());

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