Question

我有两个班：父亲和儿子。儿子延伸父亲。

两者都在重载ostream运算符。

class Father {
public:
    friend ostream& operator<<(ostream& os, Father& v); //prints "father"
};

class Son : public Father {
public:
    friend ostream& operator<<(ostream& os, Son& v); // prints "son"
};

有没有办法，从儿子我可以称为父亲＆＃34;＆lt;＆lt;＆＃34; ？

我希望儿子最终会打印出来：＆＃34;父亲的儿子＆＃34;

Answer 1

您可static_cast Son&到Father&：

class Son : public Father {
public:
    friend std::ostream& operator<<(std::ostream& os, Son& v) {
        os << static_cast<Father&>(v);
        os << "son";   
        return os;
    }
};

Answer 2

您可以使用虚拟方法覆盖。

class Father
{
public:
    virtual std::ostream& operator<<(std::ostream& os)
    {
        os << "father";
        return os;
    }
};

class Son : public Father
{
public:
    std::ostream& operator<<(std::ostream& os) override
    {
        Father::operator<<(os);
        os << " son";
        return os;
    }
};

但是，正如TartanLlama所说，这会切换运算符的参数，所以你最终会像这样使用它：

Son s;
s << std::cout;

使用父级的重载方法

2 个答案: