如果我想在函数中创建一个对象的新实例，其指针通过引用传递给它

- (void)createAString:(NSString **)str
{
   *str = [NSString stringWithString:@"Hi all!"];
   [*str autorelease]; // ???? is this right ?
}
- (void)createAString:(NSString **)str
{
   *st