Question

我有一个名为Pet的抽象类和三个派生类Cat Dog Goldfish。我试图将它们存储在矢量中并打印宠物的名字。但是我得到一些十六进制数。我不知道我在哪里做错了。

// Here is pet.h
#ifndef PET_H
#define PET_H

#include<iostream>
using namespace std;

class Pet
{
public:
    //constructor
    Pet(string);

    // virtual destructor
    virtual ~Pet();
    // pure virtual function
    virtual string speak() = 0;

    //getters setters
    string getName();

    //overloading comparative operators
    bool operator< (Pet&);
    friend ostream& operator<<(ostream&, Pet&);

protected:
    string pet_name; //name of pet
};


#endif // PET_H


Here is pet.cpp

#include <iostream>
#include "Pet.hpp"

#include <string>

using namespace std;

//constructor
Pet::Pet(string name) : pet_name(name)
{}

//overloading comparator function
bool Pet::operator<(Pet& obj)
{
    return ((pet_name.compare(obj.pet_name)) < 0);
}

//getter for name
string Pet::getName() { return pet_name; }

// destructor
Pet::~Pet() { /* dtor */ }


ostream& operator<<(ostream& output, Pet& p) {
    output << "I am pet";
    return output;
}


#ifndef CAT_H
#define CAT_H

#include "Pet.hpp"

class Cat: public Pet
{
public:
    Cat(string);
    virtual ~Cat();
    string speak();
    friend ostream& operator<<(ostream &, Cat&);
};

#endif // CAT_H


#include "Cat.hpp"
#include<string>

Cat::Cat(string name):Pet(name)
{
    //ctor
}
string Cat::speak()
{
    return ">>Meow Meow>>";
}

Cat::~Cat()
{
    //dtor
}


ostream& operator<<(ostream& output, Cat& p) {
    output << "I am " << p.getName() << " " << p.speak() << endl;
    return output;
}

List.hpp文件

#ifndef LIST_H
#define LIST_H

#include<iostream>
#include <vector>
#include<algorithm>

using namespace std;

template<class T>
class List
{
public:
    void add_item(T);
    void sortList();
    void print();

private:
    vector<T> list;
};



template<class T>
void List<T>::add_item(T item_list) {
    list.push_back(item_list);
}

template<class T>
void List<T>::sortList() {
    sort(list.begin(), list.end());
}


template<class T>
void List<T>::print() {
    std::vector<T>::iterator i;
    for (i = list.begin(); i != list.end(); ++i) {
        cout << *i << endl;
    }
}


#endif // LIST_H

这是主要功能

int main()
{
    List<Pet*> pets;
    // book items adding in the lists

    pets.add_item(new Cat("Kitty"));
    pets.add_item(new Cat("Tom"));


    // sorting lists
    pets.sortList();

    // printing lists

    // ----- Here is the PROBLEM ------
    pets.print(); // --> Here I am getting problem
    // --> when this statement executes, I get the hexa decimal number


    // saving in files
    return 0;
}

Answer 1

ftfy：

#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <memory>

class Pet
{
public:
    Pet(std::string name) : name{ std::move(name) } {}
    virtual ~Pet() = default;

    std::string get_name() const { return name; }
    virtual std::string speak() const = 0;

    friend std::ostream& operator<<(std::ostream& output, Pet const &pet)
    {
        output << "I am pet named " << pet.name;
        return output;
    }

protected:
    std::string name;
};

class Cat : public Pet
{
public:
    Cat(std::string name) : Pet{ std::move(name) } {};
    virtual ~Cat() = default;

    virtual std::string speak() const override { return ">>Meow Meow>>"; }

    friend std::ostream& operator<<(std::ostream &output, Cat const & cat)
    {
        output << "I am a cat named " << cat.name << ' ' << cat.speak();
        return output;
    }
};

class Dog : public Pet
{
public:
    Dog(std::string name) : Pet{ std::move(name) } {};
    virtual ~Dog() = default;

    virtual std::string speak() const override { return ">>Woof Woof>>"; }

    friend std::ostream& operator<<(std::ostream &output, Dog const & dog)
    {
        output << "I am a dog named " << dog.name << ' ' << dog.speak();
        return output;
    }
};

template<class T>
class List
{
public:
    void add_item(T item_list) { list.push_back(item_list); }
    void sortList() {
        std::sort(list.begin(), list.end(),
                  [](T const &lhs, T const &rhs) -> bool { return lhs.get()->get_name() < rhs.get()->get_name(); });
    }
    void print() const
    {
        for (typename std::vector<T>::const_iterator i{ list.begin() }; i != list.end(); ++i) {
            if (auto cat = dynamic_cast<Cat*>((*i).get()); cat)
                std::cout << *cat;
            else if (auto dog = dynamic_cast<Dog*>((*i).get()); dog)
                std::cout << *dog;
            else
                std::cout << **i;
            std::cout.put('\n');
        }
    }

private:
    std::vector<T> list;
};

int main()
{
    List<std::shared_ptr<Pet>> pets;
    pets.add_item(std::make_shared<Cat>("Kitty"));
    pets.add_item(std::make_shared<Cat>("Tom"));
    pets.add_item(std::make_shared<Dog>("Suzy"));
    pets.add_item(std::make_shared<Dog>("Hasso"));

    pets.sortList();
    pets.print();
}

C ++-为派生类对象打印vector <base *>元素

1 个答案: