Re: Class inheritance 101

From:

"Ben Voigt [C++ MVP]" <rbv@nospam.nospam>

Newsgroups:

microsoft.public.vc.language

Date:

Wed, 30 May 2007 09:58:52 -0500

Message-ID:

<eIs86ssoHHA.4220@TK2MSFTNGP04.phx.gbl>

"Anders Eriksson" <andis59@gmail.com> wrote in message
news:18avbydx378aj.dlg@ostling.com...

On Wed, 30 May 2007 11:51:02 +0300, Alex Blekhman wrote:

Anders Eriksson wrote:

How do I write the constructor and deconstructor for mClass so it also
calls yClass constructor and deconstructor.

It's simple:

class mClass : public yClass
{
   mClass() {}
   mClass(const mClass& other) : yClass(other)
   {
     m_x = other.m_x;
     m_y = other.m_y;
     m_pzObj = ...;
   }

   ~mClass() { /* release m_pzObj */ }

private:
   int m_x;
   int m_y;
   zClass *m_pzObj;
};

You don't need to write anything for default constructor
`mClass::mClass()'. Base class constructor will be called
automatically. The same is true for destructor.

I'm using the Thinking in C++ book and it says that constructor and
destructors will not be inherited. This I assumed meant that they will not
be called automatically. My bad ;-)

What it means is that any constructors with particular arguments will not
automatically be available in the derived class. The default constructor is
automatically available if you don't provide any other constructors, and the
automatic version calls the default constructor of the base class. Of
course, you can provide your own and do anything.

Oh, and if you are going to use polymorphism (using different derived
classes interchangably from a pointer to the base type) you will also need a
virtual destructor in the base class.

Thank you very much for your help!

// Anders
--
English is not my first, or second, language
so anything strange, or insulting, is due to
the translation.
Please correct me so I may improve my English!