Can We Access Private Data Members of a Class without using a Member or a Friend Function in C++?
The idea of Encapsulation is to bundle data and methods (that work on the data) together and restrict access of private data members outside the class. In C++, a friend function or friend class can also access private data members.
So, is it possible to access private members outside a class without friend? Yes, it is possible using pointers. Although it’s a loophole in C++, yes it’s possible through pointers.
Example 1:
CPP
#include <bits/stdc++.h>
using namespace std;
class Test {
private :
int data;
public :
Test() { data = 0; }
int getData() { return data; }
};
int main()
{
Test t;
int * ptr = ( int *)&t;
*ptr = 10;
cout << t.getData();
return 0;
}
|
Example 2:
CPP
#include <bits/stdc++.h>
using namespace std;
class A {
private :
int x;
int y;
};
int main()
{
A a;
int * p = ( int *)&a;
*p = 3;
p++;
*p = 9;
p--;
cout << endl << "x = " << *p;
p++;
cout << endl << "y = " << *p;
return 0;
}
|
Explanation: In the above program, a is an object of class A. The address of the object is assigned to integer pointer p by applying typecasting. The pointer p points to private member x. The integer value is assigned to *p, that is, x. Address of object a is increased and by accessing the memory location value 9 is assigned to y. The p– statement sets the memory location of x. Using the cout statement contains of x is displayed.
Example 3:
CPP
#include <bits/stdc++.h>
using namespace std;
class A {
private :
int x;
int y;
};
class B : public A {
public :
int z;
void show( int * k)
{
cout << "x = " << *k << " y = " << *(k + 1)
<< " z = " << *(k + 2);
}
};
int main()
{
B b;
int * p;
p = &b.z;
*p = 3;
p--;
*p = 4;
p--;
*p = 5;
b.show(p);
return 0;
}
|
Output:
x = 5 y = 4 z = 3
Note: In the above way of accessing private data members is not at all a recommended way of accessing members and should never be used. Also, it doesn’t mean that the encapsulation doesn’t work in C++. The idea of making private members is to avoid accidental changes. The above change to data is not accidental. It’s an intentionally written code to fool the compiler.
Time Complexity : O(1)
Auxiliary Space: O(1)
Last Updated :
21 Jun, 2022
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