Disallow any member function to change its data members in C++ Class

Question

So how i can do this? So that no member function can change the value of its data members once object has been initialized in C++.

Answer 1

Make all the member functions const. That's the only mechanism for the job, and it works just fine. If you also make them private you're completely covered.

If for some reason you feel compelled to mark them protected, then things are more complicated.

You will need to make the individual fields const, and that will in turn require you to initialize them via the member initialization list, or a const_cast of this in the constructor. Or maybe a mutable ctor, but I'm not sure there is such a thing.