How friend function violates the data hiding?

In object-oriented programming, data hiding is a principle that allows data to be hidden or encapsulated within a class, so that it cannot be directly accessed or modified from outside the class. This is done to ensure the integrity of the class’s data and prevent unwanted changes or errors.

A friend function is a function that is declared within a class, but is not a member function of the class. It has the special ability to access the private and protected members of the class, which would normally not be accessible from outside the class.

The use of friend functions can violate the principle of data hiding, because it allows external functions to directly access and modify the private and protected members of the class, bypassing the normal rules of encapsulation. This can lead to unintended changes or errors in the class’s data.

For example, let’s say we have a class called “BankAccount” that has private data members for the account holder’s name, account number, and balance. We also have a friend function called “withdrawMoney” that allows the account holder to withdraw money from their account.

If the “withdrawMoney” function is not carefully implemented, it could potentially allow unauthorized access to the account holder’s private data. For example, if the function does not properly validate the user’s identity or restrict the amount that can be withdrawn, it could allow someone to withdraw more money than they should or access someone else’s account information.

In general, it’s important to use friend functions with caution and only when necessary, to ensure that the principle of data hiding is not violated and the class’s data remains secure and consistent.