如何直接访问 class 的私有成员？

Question

I had a homework which i was asked how to access private members of a class and modify them in c++.I searched about it and i found out that we can do it with typecast and pointers which i know it's an undefined behavior and it should never be used.My question is: Is it possible to do such thing in other object oriented languages like java or python?

Answer 1

The C++ programming language has a friend specifier . Friend function can see its friend class' private members. But more young languages don't include this mechanism. Because the mechanism isn't correct for object oriented programming paradigm(for encapsulation).

Answer 2

In C++ you can write a member function that can access and modify private members and make such function public. This is a common way for OOP. However, of course, different languages including C++ may provide hax to modify protected members in another way.

class T {
public:
  int get() const {
    return _member;
  } 
  void set(int member) {
    _member = member;
  } 
protected:
  int _member;

};

List of well-known hacks

You can easily access any member in Python. Just dir whatever you what to hack. Private members in Python .

You can hack C++ members with template http://bloglitb.blogspot.com/2011/12/access-to-private-members-safer.html . It is much safer than use pointers.

You can access private members via reflection in Java https://docs.oracle.com/javase/tutorial/reflect/ .

Generally, any language that lets you debug the code should also reveal somehow protected variables.