How to access private data members outside the class without making friend s

Question

I have a class A as mentioned below -  class A       int iData       I neither want to create member function nor inherit the above class A nor change the specifier of iData   My doubts -   How to access iData of an object say obj1 which is an instance of class A  How to change or manipulate the iData of an object obj1    Note  Don t use friend

User · Answer

http   bloglitb blogspot com 2010 07 access-to-private-members-thats-easy html  this guy s blog shows you how to do it using templates  With some modifications  you can adapt this method to access a private data member  although I found it tricky despite having 10  years experience    I wanted to point out like everyone else  that there is an extremely few number of cases where doing this is legitimate  However  I want to point out one  I was writing unit tests for a software suite  A federal regulatory agency requires every single line of code to be exercised and tested  without modifying the original code  Due to  IMHO  poor design  a static constant was in the  private  section  but  I needed to use it in the unit test  So the method seemed to me like the best way to do it    I m sure the way could be simplified  and I m sure there are other ways  I m not posting this for the OP  since it s been 5 months  but hopefully this will be useful to some future googler

User · Answer

access private members outside  class     only for study purpose      This program accepts all the below conditions  I dont want to create member function for above class A  And also i dont want to inherit the above class A  I dont want to change the specifier of iData      here member function is used only to input and output the private values       void hack   is defined outside the class       GEEK MODE        include lt iostream h gt   include lt conio h gt       class A           private  int iData x      public  void get                 enter the values          cout lt  lt  Enter iData                  cin gt  gt iData cout lt  lt  Enter x     cin gt  gt x            void put                                   displaying values      cout lt  lt endl lt  lt  sum     lt  lt iData x       void hack             hacking function  void main    A obj clrscr    obj get   obj put   hack   obj put   getch       void hack             hack begins  int hck  ptr  amp hck  cout lt  lt endl lt  lt  Enter value of private data  iData or x       cin gt  gt hck        enter the value assigned for iData or x for int i 0 i lt 5 i     ptr    if  ptr  hck   cout lt  lt  Private data hacked       nChange the value      cin gt  gt  ptr cout lt  lt hck lt  lt   Is chaged to     lt  lt  ptr  return    cout lt  lt  Sorry value not found

User · Answer

EDIT    Just saw you edited the question to say that you don t want to use friend    Then the answer is    NO you can t  atleast not in a portable way approved by the C   standard        The later part of the Answer  was previous to the Q edit  amp  I leave it here for benefit of  those who would want to understand a few concepts  amp  not just looking an Answer to the  Question      If you have members under a Private access specifier then those members are only accessible from within the class  No outside Access is allowed   An Source Code Example   class MyClass       private          int c      public      void doSomething                 c   10       Allowed            int main         MyClass obj      obj c   30        Not Allowed  gives compiler error     obj doSomething       Allowed     A Workaround  friend to rescue To access the private member  you can declare a function class as friend of that particular class  and then the member will be accessible inside that function or class object without access specifier check   Modified Code Sample   class MyClass       private          int c       public      void doSomething                 c   10       Allowed             friend void MytrustedFriend            void MytrustedFriend             MyClass obj          obj c   10    Allowed    int main         MyClass obj      obj c   30        Not Allowed  gives compiler error     obj doSomething       Allowed       Call the friend function     MytrustedFriend        return 0

User · Answer

It s possible to access the private data of class directly in main and other s function     here is a small code     class GIFT       int i j k   public      void Fun                  cout lt  lt  i lt  lt     lt  lt  j lt  lt     lt  lt  k             int main          GIFT  obj new GIFT       the value of i j k is 0      int  ptr  int   obj        ptr 10       cout lt  lt  ptr          you also print value of I      ptr          ptr 15       cout lt  lt  ptr          you also print value of J      ptr          ptr 20        cout lt  lt  ptr          you also print value of K      obj- gt Fun

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You can t  That member is private  it s not visible outside the class  That s the whole point of the public protected private modifiers    You could probably use dirty pointer tricks though  but my guess is that you d enter undefined behavior territory pretty fast

User · Answer

friend is your friend   class A      friend void foo A arg       int iData      void foo A arg           can access a iData here     If you re doing this regularly you should probably reconsider your design though

User · Answer

There s no legitimate way you can do it

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Here s a way  not recommended though  class Weak   private      string name   public      void setName const string amp  name            this- gt name   name             string getName  const           return this- gt name             struct Hacker       string name      int main int argc  char   argv         Weak w      w setName  Jon        cout  lt  lt  w getName    lt  lt  endl      Hacker  hackit   reinterpret cast lt Hacker   gt   amp w       hackit- gt name    Jack       cout  lt  lt  w getName    lt  lt  endl

User · Answer

Bad idea  don t do it ever - but here it is how it can be done   int main        A aObj     int  ptr      ptr    int   amp aObj         MODIFY      ptr   100

User · Answer

In C    almost everything is possible  If you have no way to get private data  then you have to hack  Do it only for testing   class A        int iData      int main          A a      struct ATwin   int pubData        define a twin class with public members     reinterpret cast lt ATwin  gt    amp a  - gt pubData   42     set or get value      return 0

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Start making friends of class A  e g   void foo      class A    int iData    friend void foo          Edit   If you can t change class A body then A  iData is not accessible with the given conditions in your question

User · Answer

iData is a private member of the class  Now  the word private have a very definite meaning  in C   as well as in real life  It means you can t touch it  It s not a recommendation  it s the law  If you don t change the class declaration  you are not allowed to manipulate that member in any way  shape or form

[c++] How to access private data members outside the class without making "friend"s?

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