Re: Not sure how this program compiles without any error.

From:

tonydee <tony_in_da_uk@yahoo.co.uk>

Newsgroups:

comp.lang.c++

Date:

Mon, 12 Apr 2010 00:59:12 -0700 (PDT)

Message-ID:

<12e85947-9295-403c-87b2-776dbbed3993@x3g2000yqd.googlegroups.com>

On Apr 12, 4:25 pm, Suresh V <vsuresh...@gmail.com> wrote:

#include <iostream.h>

class A {
    protected:
        int a;
};

class B : protected A
{ };

class C: private B
{
   public:
       void assign() {
           a = 1;
       }
};

int main(){
    C* a = new C();
    a->assign();
}

How can class 'C' has access to Class 'A' data members if class 'C' is
derived as private from class 'B' which intern derives class 'A' as
protected ? please help

The way to read this is:
- Class A only grants access to 'a' to derived classes
- Class B is derived from A (hence it can access 'a'), and only grants
access to A (and hence 'a') to its own derived/sub-classes
- Class C is derived from B (hence it can access 'a'), but will keep A
(and hence 'c') hidden from even its derived classes

So, those access specifiers relate to how the base class's members are
exposed to the _next_ level of derived class. Consequently, if you
subclass C, it will not have access to 'a'.

Cheers,
Tony