1

I'm confused on how private variables are inherited and I'm getting errors telling my variable's are private when I try to use them in inherited classes.

A bare-bones example.

Let's say:

//dog.h
class dog
{
private:
    bool fluffy;
public:
    ...
};

And let's say:

//dog.cpp
#include "dog.h"
...

Now:

//shepard.h
#include "dog.h"
class shepard: public dog
{
private:
    ...
public:
    void groom();
};

And:

//shepard.cpp
#include "shepard.h"
void shepard::groom()
{
    fluffy = false;
}

If I try to use the groom function I get an error something like:

error: 'bool dog::fluffy' is private

What am I doing wrong? Optional: What's the best way to design this solution in the future?

Pham Trung
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Willy Goat
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    Subclasses don't get access to superclasses `private` variables - that's what makes them `private`. You need to make them `protected` to do what you want. +1 for deriving shepherd from dog, though. – Crowman Sep 23 '14 at 02:11

1 Answers1

2

The most important rule for inheritance is:

Private members of a class are never accessible from anywhere except the members of the same class.

Further in Private Inheritance:

All Public members of the Base Class become Private Members of the Derived class &
All Protected members of the Base Class become Private Members of the Derived Class

Good Read:
What are access specifiers? Should I inherit with private, protected or public?

Community
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Alok Save
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    @WillyGoat: Added a link of my previous answer for you to understand access specifiers & inheritance. Once you read it you can *understand* them better and decide for yourself what you need to use. – Alok Save Sep 23 '14 at 02:14