Re: [boost] Request for data-member smart pointer

6 Oct 2004


      Oleg Fedtchenko wrote:
...
To Peter Dimov
Hi, Peter
Could you, please, tell if is there a smart pointer template to a
class data-member.
I failed to find  an appropriate pointer among five ones existing in
the boost.
I need it for the two tasks appended.
No, none of the existing pointers address the problem directly, although 
shared_ptr can be persuaded to do what you want.
...
Task 2)
class DocActiveX
{
protected:
   Tree* m_pTree;
public:
   ~DocActiveX(){ if(m_pTree) delete m_pTree;}
   bool Load( const char* lpszPath);
   Tree* Parse(){ return m_pTree;}
};
That's the easy part.

class DocActiveX
{
private:

    shared_ptr<Tree> m_pTree;

public:

    bool Load( const char* lpszPath );
    shared_ptr<Tree> Parse() { return m_pTree; }
};
...
Task 1)
class A
{
public:
   A(){ m_wData = 0;}
   WORD* GetData(){ return &m_wData}
   A* CreateA( int nOffset){ return new A;}
protected:
   WORD m_wData;
};
This is a bit harder.

class A
{
private:

    WORD m_wData;

private:

    A();

public:

    static shared_ptr<A> CreateA() { return shared_ptr<A>(new A); }

    friend shared_ptr<WORD> GetData( shared_ptr<A> this_ )
    {
        return shared_ptr<WORD>(
            &this_->m_wData,
            boost::bind( &shared_ptr<A>::reset, this_ )
        );
    }
};

int main()
{
    shared_ptr<A> pa = A::CreateA();
    shared_ptr<WORD> pw = GetData(pa);
    pa.reset();
    std::cout << "*pw: " << *pw << '\n';
}