c++ - 继承中的istream和ostream

Question

我有两个类:

class a{
    friend istream &operator>> (istream&in, a&ob) { }
    friend ostream &operator<< (ostream&out, const a&ob) { }
}

class b:public a{
    friend istream &operator>> (istream&in, b&ob) { }
    friend ostream &operator<< (ostream&out, const b&ob) { }
}

A 类效果很好。我可以读取和写入 a 类型的对象。 b 类继承了 a 类的所有内容并添加了一些新数据。在我的 b 类 istream 和 ostream 运算符中，有没有办法使用 a 类的输入/输出运算符来读写公共(public)字段？谢谢。

Answer 1

您可以通过将 ob 转换为父类(super class)的类型来重用运算符:

ostream &operator<< (ostream& out, const b& ob) {
   // Output the parts common to a and b
   out << static_cast<const a&>(ob);
   // Do additional things specific to b
   out << some_part_specific_to_b;
   return out;
}