Question

在练习C ++基本继承概念时，遇到了打印自定义类对象并写入重载的需要，紧接着指南仍然没有注册使用新运算符进行打印（＆lt;＆lt;＆lt;）。

我想知道输入不正确或在其他地方有一些声明/启动错误吗？

不匹配'operator＆lt;＆lt;'（操作数类型是 'std :: basic_ostream'和'Choco'）std :: cout＆lt;＆lt; ＆＃34;巧克力价值：＆＃34; ＆LT;＆LT;孩子＆lt;＆lt; ENDL;

#include <iostream>
using namespace std;

class Sweets {
        public:
                // pure virtual, child MUST implement or become abstract
                // Enclosing class becomes automatically abstract - CANNOT instantiate
                virtual bool eat() = 0;
};

// public inheritance : public -> public, protected -> protected, private only accessible thru pub/pro members
class Choco : public Sweets {
        public:

                bool full;

                Choco() {
                        full = false;
                }

                // Must implement ALL inherited pure virtual
                bool eat() {
                        full = true;
                }

                // Overload print operator
                bool operator<<(const Choco& c) {
                        return this->full;
                }
};

int main() {

// Base class object
//sweets parent;
Choco child;

// Base class Ptr
// Ptr value = address of another variable
Sweets* ptr; // pointer to sweets
ptr = &child;

std::cout<< "Sweets* value:  " << ptr << endl;
std::cout<< "Choco address: " << &child << endl;
std::cout<< "Choco value: " << child << endl; // Printing causes error!
}

Answer 1

运算符在类外定义如下，因为它不是类成员。

std::ostream & operator <<( std::ostream &os, const Choco &c ) 
{
    return os << c.full;
}

考虑到功能

bool eat() {
    full = true;
}

应该有一个带有bool类型表达式的return语句，或者它应该在基类和派生类中使用返回类型void声明。

打印操作员过载失败？

1 个答案: