Here, we will discuss scope of the variables and functions declared in a base class and derived class. To illustrate this, let us take an example.
First, we deine a class
A
, which contains three variables having different visibility scope.
Then we define a subclass
B
which inherits the base class
A
using
public
scope.
We have commented the lines where variables are not accesssible.
#include <iostream>
using namespace std;
class A{
private:
int a = 10;
protected:
int b = 20;
public:
int c = 30;
void print(){
cout << a << endl;
cout << b << endl;
cout << c << endl;
}
};
class B : public A {
private:
int x = 11;
protected:
int y = 22;
public:
int z = 33;
void print(){
//cout << a << endl;
cout << b << endl;
cout << c << endl;
cout << x << endl;
cout << y << endl;
cout << z << endl;
}
};
int main(void){
A a;
a.print();
B b;
b.print();
//cout << a.a << endl;
//cout << a.b << endl;
cout << a.c << endl;
//cout << b.a << endl;
//cout << b.b << endl;
cout << b.c << endl;
//cout << b.x << endl;
//cout << b.y << endl;
cout << b.z << endl;
return 0;
}
If the class
B
inherits class
A
in protected mode, the variables and functions having
public
access in base class are inherited as protected members. Thus,
accessibility change is shown in the follwing code.
#include <iostream>
using namespace std;
class A{
private:
int a = 10;
protected:
int b = 20;
public:
int c = 30;
void print(){
cout << a << endl;
cout << b << endl;
cout << c << endl;
}
};
class B : protected A {
private:
int x = 11;
protected:
int y = 22;
public:
int z = 33;
void print(){
//cout << a << endl;
cout << b << endl;
cout << c << endl;
cout << x << endl;
cout << y << endl;
cout << z << endl;
}
};
int main(void){
A a;
a.print();
B b;
b.print();
//cout << a.a << endl;
//cout << a.b << endl;
cout << a.c << endl;
//cout << b.a << endl;
//cout << b.b << endl;
//cout << b.c << endl;
//cout << b.x << endl;
//cout << b.y << endl;
cout << b.z << endl;
return 0;
}
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