2.2 KiB
[class.nest]
11 Classes [class]
11.4 Class members [class.mem]
11.4.12 Nested class declarations [class.nest]
A class can be declared within another class.
A class declared within another is called a nested class.
[Note 1:
See [expr.prim.id] for restrictions on the use of non-static data members and non-static member functions.
â end note]
[Example 1: int x;int y;
struct enclose {int x; static int s; struct inner {void f(int i) {int a = sizeof(x); // OK, operand of sizeof is an unevaluated operand x = i; // error: assign to enclose::x s = i; // OK, assign to enclose::s::x = i; // OK, assign to global x y = i; // OK, assign to global y}void g(enclose* p, int i) { p->x = i; // OK, assign to enclose::x}};};
inner* p = 0; // error: inner not found â end example]
[Note 2:
Nested classes can be defined either in the enclosing class or in an enclosing namespace; member functions and static data members of a nested class can be defined either in the nested class or in an enclosing namespace scope.
[Example 2: struct enclose {struct inner {static int x; void f(int i); };};
int enclose::inner::x = 1;
void enclose::inner::f(int i) { /* ... */ }class E {class I1; // forward declaration of nested classclass I2; class I1 { }; // definition of nested class};class E::I2 { }; // definition of nested class â end example]
â end note]
A friend function ([class.friend]) defined within a nested class has no special access rights to members of an enclosing class.