Can static member function of base class call its derived class object? (C++)

Can sta开发者_StackOverflowtic member function of base class call its derived class object?

Think of static member-function as some non-member function. So yes. Whatever non-member function can do, static member-function can do the very same thing!

Yes, though there are two things to watch out for.

The first is forward-references. If the code to your static method is in the .cpp file, you should be able to safely #include the base and derived class headers.

<Base.h>
class Base
{
protected:
    Base();
public:
    virtual ~Base();

    static Base* Create();
};

<Derived.h>
#include "Base.h"
class Derived : public Base
{
public:
    Derived(int aParameterGoesHere);
};

<Base.cpp>
#include "Base.h"
#include "Derived.h"

Base::Base() { }
Base::~Base() { }

Base* Base::Create()
{
    return new Derived(42);
}

The second thing to watch for is that private/protected members of Derived are not accessible from Base unless they were declared as virtual members of Base or Base is declared a friend class of Derived (which is not unreasonable, considering the tight coupling):

<Derived.h>
#include "Base.h"
class Derived : public Base
{
    friend Base;
private:
    Derived(int aParameterGoesHere);
};

No, it can not call, because a static member function has no object assigned to it, therefore it has no its derived class object.

However, it is possible if you are using CRTP, like this :

template< T >
struct base
{
  base()
  {
    T::foo();   // here calling a static method of derived class
  }
  virtual ~base(){}
};

struct A : base< A >
{
  virtual ~A(){}
  static void foo()
  {
    // do stuff
  }
};