Question

我尝试执行以下操作：我有Person类，我希望能够使用抽象Animal类的任何类型的实现，所以我希望能够在main方法中创建多个人，这些人中的每一个都能够使用任何一种狗或猫等，这些人应该使用特定狗，猫等的doSomething（）方法的具体实现。现在的实现不起作用，我知道，编译器当然说，动物不能使用doSomething（）方法（因为它的虚拟）。我怎样才能实现我在这里尝试做的事情？

person.h

#include <animal.h>

class Person
{
public:
    Person();
    ~Person();
    Animal *ani;
};

Person::Person (Animal *pointer) 
{
  ani = new Animal ();
}

Person::SomeMethod ()
{
  ani->doSomething ();
}

Person::~Person ()
{
  delete ani;
}

animal.h

class Animal
{
public:
    Animal();
    ~Animal();
    virtual void doSomething () = 0; 
};

class Dog : public Animal
{
public:
    Dog();
    ~Dog();
    void doSomething ();
};

Dog::Dog ()
{
  std::cout << "I've been created!" << std::endl;
}

Dog::doSomething ()
{
  std::cout << "Hello" << std::endl;
}

main.h

#include <animal.h>
#include <person.h>

int main()
{
    Dog *bowser;
    Person *will = new Person (bowser);
    return 0;
}

Answer 1

以下是Person接受任何Animal：

的示例

#include <iostream>

class Animal
{
public:
    Animal() = default;
    virtual ~Animal() {};
    virtual void doSomething() = 0;
};

class Person
{
public:
    Person(Animal* pointer); 
    ~Person();

    void SomeMethod();
    Animal *ani;
};

Person::Person(Animal *pointer)
    : ani{pointer} // initialize from passed pointer
{
    //ani = new Animal(); //Person doesn't create/own an animal
}

void Person::SomeMethod()
{
    ani->doSomething();
}

Person::~Person()
{
    //delete ani; // Person doesn't own animal
}

class Dog : public Animal
{
public:
    Dog();
    ~Dog() = default;
    void doSomething();
};

Dog::Dog()
{
    std::cout << "I've been created!" << std::endl;
}

void Dog::doSomething()
{
    std::cout << "Hello" << std::endl;
}

int main()
{
    Dog bowser; // no new here, RAII will take care of killing the Dog
    Dog* bowser_ptr = &bowser;
    Person will(bowser_ptr);
    will.SomeMethod();
    return 0;
}

以下是Person拥有随机Animal：

的示例

#include <vector>
#include <iostream>
#include <random>
#include <exception>

class Animal
{
public:
    Animal() = default;
    virtual ~Animal() {}; // must be virtual!
    virtual void doSomething() = 0;
};

class Dog : public Animal
{
public:
    Dog();
    ~Dog();
    void doSomething();
};


class Cat : public Animal
{
public:
    Cat();
    ~Cat();
    void doSomething();
};

Animal* get_random_animal()
{
    static std::random_device rd;
    static std::mt19937 gen(rd());
    static std::uniform_int_distribution<> dis(1, 2);
    switch(dis(gen)) {
        case 1:
            return new Dog;
        case 2:
            return new Cat;
        default:
            throw std::runtime_error{"Not sure which animal."};
    }
}

class Person
{
public:
    Person(); 
    Person(Person&&) = delete; // person contains raw pointers, we must either delete or specify the move constructor
    Person(const Person&) = delete; // person contains raw pointers, we must either delete or specify the copy constructor
    Person& operator=(Person&&) = delete; // person contains raw pointers, we must either delete or specify the move assignment operator
    Person& operator=(const Person&) = delete; // person contains raw pointers, we must either delete or specify the copy assignment operator
    ~Person();

    void SomeMethod();
    Animal *ani;
};

Person::Person()
    : ani{get_random_animal()} // initialize with random animal
{

}

void Person::SomeMethod()
{
    ani->doSomething();
}

Person::~Person()
{
    delete ani; // Person does own animal
}


Dog::Dog()
{
    std::cout << "I've been created! Woof!" << std::endl;
}

Dog::~Dog()
{
    std::cout << "I've been destroyed! Woof!" << std::endl;
}

void Dog::doSomething()
{
    std::cout << "Woof" << std::endl;
}


Cat::Cat()
{
    std::cout << "I've been created! Meow!" << std::endl;
}

Cat::~Cat()
{
    std::cout << "I've been destroyed! Meow!" << std::endl;
}

void Cat::doSomething()
{
    std::cout << "Meow" << std::endl;
}

int main()
{
    Person will;
    will.SomeMethod();

    std::cout << "\n More people with animals: \n";
    std::vector<Person> people(10);
    return 0;
}

示例输出：

I've been created! Meow!
Meow

 More people with animals:
I've been created! Woof!
I've been created! Meow!
I've been created! Meow!
I've been created! Meow!
I've been created! Meow!
I've been created! Meow!
I've been created! Woof!
I've been created! Meow!
I've been created! Woof!
I've been created! Woof!
I've been destroyed! Woof!
I've been destroyed! Meow!
I've been destroyed! Meow!
I've been destroyed! Meow!
I've been destroyed! Meow!
I've been destroyed! Meow!
I've been destroyed! Woof!
I've been destroyed! Meow!
I've been destroyed! Woof!
I've been destroyed! Woof!
I've been destroyed! Meow!

在另一个类中使用成员方法＆＃34;通常＆＃34;

person.h

animal.h

main.h

1 个答案: