can a class grant access to a friend method of friend class?

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title was self explanatory..

i repeat ..

can a class allow a friend method of a friend class to use it's protected or private members

oh yes one more,

can a friend method of a derived class use base class's protected members

i am new to this type of concept
please help

thanks in advance

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tnvkrishna

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Nov 7th, 2007

Re: can a class grant access to a friend method of friend class?

>can a class allow a friend method of a friend class to use it's protected or private members
Just because you're my friend doesn't mean your other friends are also my friends.

>can a friend method of a derived class use base class's protected members
If you're my child, your friends aren't necessarily my friends.

Narue

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Nov 8th, 2007

Re: can a class grant access to a friend method of friend class?

>> can a friend method of a derived class use base class's protected members
friend functions have the same access rights as the members of the class. a derived class can access (only) inherited protected members of the base class. if a derived class can access the base class's protected members, friends of the derived class can access them too. and if a derived class cannot access the base class's protected members (because it has not inherited them), friends of the derived class also cannot access them. for example:

c++ Syntax (Toggle Plain Text)
struct base_class
{
  protected: int protected_member ;
};
 
struct derived_class : base_class
{
  void member_function( derived_class& derived, base_class& base )
  {
     derived.protected_member = 9 ; // ok, inherited by derived_class
     derived.base_class::protected_member = 9 ; // also ok, inherited
     base.protected_member = 9 ; // error, not inherited by derived_class
  }
  friend inline void friend_function( derived_class& derived, 
                                     base_class& base )
  {
     derived.protected_member = 9 ; // ok, inherited by derived_class
     derived.base_class::protected_member = 9 ; // also ok, inherited
     base.protected_member = 9 ; // error, not inherited by derived_class
  }
};
struct base_class
{
  protected: int protected_member ;
};

struct derived_class : base_class
{
  void member_function( derived_class& derived, base_class& base )
  {
     derived.protected_member = 9 ; // ok, inherited by derived_class
     derived.base_class::protected_member = 9 ; // also ok, inherited
     base.protected_member = 9 ; // error, not inherited by derived_class
  }
  friend inline void friend_function( derived_class& derived, 
                                     base_class& base )
  {
     derived.protected_member = 9 ; // ok, inherited by derived_class
     derived.base_class::protected_member = 9 ; // also ok, inherited
     base.protected_member = 9 ; // error, not inherited by derived_class
  }
};

Last edited by vijayan121; Nov 8th, 2007 at 3:51 am.

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