1@protocol P @end 2 3@interface NSMutableArray 4- (id)objectAtIndexedSubscript:(unsigned int)index; 5- (void)setObject:(id)object atIndexedSubscript:(unsigned int)index; 6@end 7 8@interface NSMutableDictionary 9- (id)objectForKeyedSubscript:(id)key; 10- (void)setObject:(id)object forKeyedSubscript:(id)key; 11@end 12 13void all() { 14 NSMutableArray *array; 15 id oldObject = array[10]; 16 17 array[10] = oldObject; 18 19 NSMutableDictionary *dictionary; 20 id key; 21 id newObject; 22 oldObject = dictionary[key]; 23 24 dictionary[key] = newObject; 25} 26 27