Page 115 - DCAP404 _Object Oriented Programming

Object-oriented Programming

Notes class C;
class A {
class B { // arbitrary nested class definitions
friend class C;
};
};
If the friend function is a member of another class, you need to use the scope resolution operator
(::).

Example:
class A {
public:
int f() { }
};
class B {

friend int A::f();
};
Friends of a base class are not inherited by any classes derived from that base class. The following
example demonstrates this:

class A {
friend class B;
int a;
};
class B { };
class C : public B {
void f(A* p) {

// p->a = 2;
}
};
The compiler would not allow the statement p->a = 2 because class C is not a friend of class A,
although C inherits from a friend of A.

Friendship is not transitive. The following example demonstrates this:
class A {
friend class B;
int a;
};
class B {
friend class C;

108 LOVELY PROFESSIONAL UNIVERSITY