C++ 友谊

2024-04-12 05:32:02 512

示例

该friend关键字是用来给其他类和函数访问类的private和protected成员，甚至通过他们的class`s范围之外定义。

class Animal{
private:
    double weight;
    double height;
public:
    friend void printWeight(Animal animal);
    friend class AnimalPrinter;
    // A common use for a friend function is to overload the operator<< for streaming. 
    friend std::ostream& operator<<(std::ostream& os, Animal animal);
};

void printWeight(Animal animal)
{
    std::cout <<animal.weight<< "\n";
}

class AnimalPrinter
{
public:
    void print(const Animal& animal)
    {
        // Because of the `friend class AnimalPrinter;" declaration, we are
        //允许在这里访问私有成员。
        std::cout <<animal.weight<< ", " <<animal.height<< std::endl;
    }
}

std::ostream& operator<<(std::ostream& os, Animal animal)
{
    os << "动物身高： " <<animal.height<< "\n";
    return os;
}

int main() {
    Animal animal = {10, 5};
    printWeight(animal);

    AnimalPrinter aPrinter;
    aPrinter.print(animal);

    std::cout << animal;
}

10
10, 5
动物身高： 5

C++ 友谊

示例

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