如何使用重载打印 derived class 的一些特定属性 <<

Question

我有一个名为 Animals 的基础 Class 和 2 个派生的 class Dog 和 Cat

class Animal{

protected:
    std::string name;
    std::string color;
public:
    std::string getName() {
        return name;
    }

    std::string getColor() {
        return color;
    }
...

class Cat : public Animal {
private :
    int lives;
public :
    int getLives() {
        return lives;
    }
...

class Dog : public Animal {
private :
    std::string gender;

public:
    std::string getGender(){
        return gender;
    }
...

我有 shared_ptr

的 vec

std::vector<std::shared_ptr<Animal>> animals

我在向量中添加了一些猫和狗，我试图从向量中打印出每只动物的所有特征，使用运算符>>（这是一项作业，我们必须使用它）我做到了这个

template <typename T>
std::ostream& operator<<(std::ostream& os, const std::vector<std::shared_ptr<T>>& v)
{

    for (int i = 0; i < v.size(); ++i) {
        os << v[i]->getName();
        os << "-";
        os << v[i]->getColor();
        if (i != v.size() - 1)
            os << ", ";
            os<<"\n";
    }

    return os;
}

但这样我只能打印名称和颜色或动物（这些属性在基础中class）我的问题是：我如何打印所有属性，猫的生命和狗的性别？？？

Answer 1

试试这个：

class Animal {

protected:
    std::string name;
    std::string color;
public:

    virtual void print(std::ostream& os){
        os << "Name:" << name <<" Color:"<< color;
    }

    void setName(string n) { name = n; }
    void setColor(string c) { color = c; }
    std::string getName() {
        return name;
    }

    std::string getColor() {
        return color;
    }
};
class Cat : public Animal {
private:
    int lives;
public:
    void setLives(int n) { lives = n; }
    void print(std::ostream& os) {
        Animal::print(os);
        os <<" Lives:"<<lives;
    }
    int getLives() {
        return lives;
    }
};
class Dog : public Animal {
private:
    std::string gender;  
public:
    void setGender(string g) { gender = g; }
    void print(std::ostream& os) {
        Animal::print(os);
        os << " Gender:" << gender;
    }
    std::string getGender() {
        return gender;
    }
};  
template <typename T>
std::ostream& operator<<(std::ostream& os, const std::vector<std::shared_ptr<T>>& v)
{
    for (int i = 0; i < v.size(); ++i) {
        v[i]->print(os);
        os << "\n";
    }   
    return os;
}    
int main()
{
    shared_ptr<Dog> d1 = make_shared<Dog>();
    d1->setName("Dog1"); d1->setColor("White"); d1->setGender("Male");
    shared_ptr<Cat> c1 = make_shared<Cat>();
    c1->setName("Cat1"); c1->setColor("Brown"); c1->setLives(1);
    vector<shared_ptr<Animal>> vec;
    vec.push_back(d1);
    vec.push_back(c1); 
    cout << vec;   
    return 0;
}

如何使用重载打印 derived class 的一些特定属性 <<

How to print some specific atributes of derived class using overload <<

c++

sharepoint

overloading

derived-class