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问题的结构是这样的 Food 是一个抽象基类；Plant 和 Animal 直接继承自它。草食动物、肉食动物和杂食动物继承自动物，而水果、坚果和树叶继承自植物狐猴、考拉和松鼠继承草食动物

总的来说，这是一团糟，但对于锻炼来说是必要的。整个项目在 GitHub 上可用 https://github.com/joekitch/OOP_JK_Assignment_4/blob/master/OOP_JK_Assignment_4/Lemur.h 完整的类图也在 GitHub 上

但这里有一些相关的东西（至少，我认为是相关的）首先是食物类，它几乎什么都没有

#pragma once
#include <string>
#include <list>
using namespace std;

class Food
{
public:

    Food(){ }
    virtual ~Food(){ }


};

接下来是Animal，它包含了hunt()和eat()函数的虚函数

#pragma once
#include "Food.h"
#include "Animal.h"
#include "Plant.h"
#include <iostream>
#include <string>
#include <list>
using namespace std;

class Animal : public Food
{
public:
    Animal(void) : name(), alive(true), age(0), calories(0), weight(0) { }
        Animal(string& animal_name, int animal_age, int animal_calories, double animal_weight) : 
        name(animal_name), alive(true), age(animal_age), calories(animal_calories), weight(animal_weight), maxcalories(animal_calories) {}

    virtual ~Animal(){}

    virtual bool eat(Food* food){return false;};
    virtual bool hunt(list<Food*> &foodlist){return false;};


    virtual void PrintSelf(){};

    virtual string& getName(){
        return name;
    };


        std::string name;
        bool alive;
        int age, calories, maxcalories;
        double weight;
};

这是 Herbivore，它完全定义了 hunt() 函数，这就是问题开始的地方（请参阅我在 hunt() 中的评论）。Hunt 接收一个 Food* 类型的列表，该列表在 main() 中全局声明

#pragma once
#include "Animal.h"
//#include "Lemur.h"
#include "Plant.h"
#include "Fruit.h"
#include "Leaf.h"
#include "Nut.h"
#include <iostream>
#include <string>
#include <list>
#include <typeinfo>
using namespace std;

class Herbivore : public virtual Animal
    {
    public:
        Herbivore() {}
        virtual ~Herbivore(){}
        virtual bool eat(Food* food) {cout << "herbivore.h eat() called" << endl; return true;};



        bool hunt(list<Food*> &foodlist) //herbivore version of hunt()
        {
            int fruitcounter=0;
            int plantcounter=0;
            string name;
            for (list<Food*>::iterator it = foodlist.begin(); it != foodlist.end(); it++)
            {
                if (Plant* temp = dynamic_cast<Plant*>(*it))
                {
//this is there the problems start. the above dynamic cast SHOULD make temp 
//non-null if the thing i'm looking at is a child of plant (that is, if the thing 
//in the food list is a fruit or a nut or a leaf). And indeed it does...but the 
//next dynamic cast (in the eat() function of Lemur) doesn't detect any fruits....

                    plantcounter++;

                    if ( eat(*it) )
                    fruitcounter++;
                    //return true;
                }

            }
            cout << "there are " << fruitcounter << " fruits and " << plantcounter << " plants in the list." << endl;
            return false;
        };


};

这是水果类。没什么特别值得注意的，我只是把它放在这里以防万一它们有助于解决问题

#pragma once
#include <iostream>
#include <string>
#include "Plant.h"
using namespace std;

class Fruit : public Plant {
    public:
        Fruit (std::string& plant_name, int energy_value):
          Plant (plant_name, energy_value){} //constructor pased to base class

        ~Fruit(){ } //destructor

        //inherits basically everything from the Plant base class, makes leae nodes in the class tree easy to write and access



    };

现在这是真正的麻烦制造者。这只狐猴完全定义了eat()函数，并从hunt()传递给它的Food*，从草食动物调用，并对其进行更多测试以查看它是否是水果（这是唯一种植狐猴可以吃）

#pragma once
#include "Animal.h"
#include "Herbivore.h"
#include "Plant.h"
#include "Fruit.h"
#include "Leaf.h"
#include "Nut.h"
#include <iostream>
#include <string>
#include <list>
#include <typeinfo>
using namespace std;

class Lemur : public Herbivore
{
    public:
        Lemur(void) : name(), alive(true), age(0), calories(0), weight(0) {}
        Lemur(string& animal_name, int animal_age, int animal_calories, double animal_weight) : 
        name(animal_name), alive(true), age(animal_age), calories(animal_calories), weight(animal_weight), maxcalories(animal_calories) {}


        ~Lemur(){}



        bool eat(Food* food)
        {




            if (Fruit* temp = dynamic_cast<Fruit*>(food))
            {
                //PROBLEM, it sees every plant as a fruit in this
//case...at least according to a typeinfo().name() that i have run in here. However the temp
//always returns null, so this proper if statement never actually happens, so it never sees
//any fruit, even though there's a whole bunch in the list (500 of them). what's wrong?
                cout << "it's a fruit" << endl;
                return true;
            }
            else
            {
                //cout << "not a fruit" << endl;
                return false;
            }


        }


    void PrintSelf()
    {
        cout << "i am a " << age << " year old, " << weight << " kilogram " << name << " with " << calories << " calories." << endl;
    };

    string& getName(){
        return name;
    };

        std::string name;
        bool alive;
        int age, calories, maxcalories;
        double weight;


};

如您所见，即使我已经确认它遍历列表，dynamic_cast 也永远不会返回非空临时值。我还使用计数器变量来跟踪它的进度，奇怪的是它说列表中有 1500 种植物……但是 0 种水果……

我的演员表结构错了吗？我的继承权取消了吗？做什么？

编辑; 我为每个类添加了虚拟析构函数，所以这不是问题

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1 回答 1

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从查看 github 存储库，看起来问题出main.cpp在您将对象添加到的位置Food_list：

else if (FileIn_type == Plant_type)
{
    Plants++;
    FileIn >> FileIn_name >> FileIn_calories;
    Food_list.push_back(new Plant (FileIn_name, FileIn_calories) );
}

您只需要创建一个Plant对象以添加到列表中。这就是所有这些对象的动态类型。

就在 中的那段代码之上main.cpp，您有一系列if/else语句，它们根据动物名称字符串创建不同的动物类型。你需要为植物做类似的事情。

于 2013-05-10T07:58:49.030 回答