Page 116 - DCAP404 _Object Oriented Programming

Unit 5: Static Members

}; Notes
class C {
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 is a friend of A.
If you declare a friend in a local class, and the friend’s name is unqualified, the compiler will
look for the name only within the innermost enclosing nonclass scope. You must declare a
function before declaring it as a friend of a local scope. You do not have to do so with classes.

Notes Note that a declaration of a friend class will hide a class in an enclosing scope with
the same name.

The following example demonstrates this:

class X { };
void a();
void f() {
class Y { };
void b();
class A {

friend class X;
friend class Y;
friend class Z;
// friend void a();
friend void b();
// friend void c();
};
::X moocow;
// X moocow2;

}
In the above example, the compiler will allow the following statements:
1. friend class X: This statement does not declare ::X as a friend of A, but the local class X as a
friend, even though this class is not otherwise declared.

2. friend class Y: Local class Y has been declared in the scope of f().
3. friend class Z: This statement declares the local class Z as a friend of A even though Z is not
otherwise declared.

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