实验五

任务一：

1.源代码：

（1）publisher.hpp:

#pragma once

#include <string>

// 发行/出版物类：Publisher （抽象类）
class Publisher {
public:
    Publisher(const std::string &name_ = "");            // 构造函数
    virtual ~Publisher() = default;

public:
    virtual void publish() const = 0;                 // 纯虚函数，作为接口继承
    virtual void use() const = 0;                     // 纯虚函数，作为接口继承

protected:
    std::string name;    // 发行/出版物名称
};

// 图书类: Book
class Book: public Publisher {
public:
    Book(const std::string &name_ = "", const std::string &author_ = "");  // 构造函数

public:
    void publish() const override;        // 接口
    void use() const override;            // 接口

private:
    std::string author;          // 作者
};

// 电影类: Film
class Film: public Publisher {
public:
    Film(const std::string &name_ = "", const std::string &director_ = "");   // 构造函数

public:
    void publish() const override;    // 接口
    void use() const override;        // 接口            

private:
    std::string director;        // 导演
};


// 音乐类：Music
class Music: public Publisher {
public:
    Music(const std::string &name_ = "", const std::string &artist_ = "");

public:
    void publish() const override;        // 接口
    void use() const override;            // 接口

private:
    std::string artist;      // 音乐艺术家名称
};

（2）publisher.cpp:

#include <iostream>
#include <string>
#include "publisher.hpp"

// Publisher类：实现
Publisher::Publisher(const std::string &name_): name {name_} {
}


// Book类: 实现
Book::Book(const std::string &name_ , const std::string &author_ ): Publisher{name_}, author{author_} {
}

void Book::publish() const {
    std::cout << "Publishing book《" << name << "》 by " << author << '\n';
}

void Book::use() const {
    std::cout << "Reading book 《" << name << "》 by " << author << '\n';
}


// Film类：实现
Film::Film(const std::string &name_, const std::string &director_):Publisher{name_},director{director_} {
}

void Film::publish() const {
    std::cout << "Publishing film <" << name << "> directed by " << director << '\n';
}

void Film::use() const {
    std::cout << "Watching film <" << name << "> directed by " << director << '\n';
}


// Music类：实现
Music::Music(const std::string &name_, const std::string &artist_): Publisher{name_}, artist{artist_} {
}

void Music::publish() const {
    std::cout << "Publishing music <" << name << "> by " << artist << '\n';
}

void Music::use() const {
    std::cout << "Listening to music <" << name << "> by " << artist << '\n';
}

（3）task1.cpp:

#include <memory>
#include <iostream>
#include <vector>
#include "publisher.hpp"

void test1() {
   std::vector<Publisher *> v;

   v.push_back(new Book("Harry Potter", "J.K. Rowling"));
   v.push_back(new Film("The Godfather", "Francis Ford Coppola"));
   v.push_back(new Music("Blowing in the wind", "Bob Dylan"));

   for(Publisher *ptr: v) {
        ptr->publish();
        ptr->use();
        std::cout << '\n';
        delete ptr;
   }
}

//void test2() {
//    std::vector<std::unique_ptr<Publisher>> v;
//
//    v.push_back(std::make_unique<Book>("Harry Potter", "J.K. Rowling"));
//    v.push_back(std::make_unique<Film>("The Godfather", "Francis Ford Coppola"));
//    v.push_back(std::make_unique<Music>("Blowing in the wind", "Bob Dylan"));
//
//    for(const auto &ptr: v) {
//        ptr->publish();
//        ptr->use();
//        std::cout << '\n';
//    }
//}

void test3() {
    Book book("A Philosophy of Software Design", "John Ousterhout");
    book.publish();
    book.use();
}

int main() {
    std::cout << "运行时多态：纯虚函数、抽象类\n";

    std::cout << "\n测试1: 使用原始指针\n";
    test1();

//    std::cout << "\n测试2: 使用智能指针\n";
//    test2();

    std::cout << "\n测试3: 直接使用类\n";
    test3();
}

（注：由于使用编译器是DevC++，版本较低，导致不能够使用注释掉的部分（智能指针部分））；

2.运行代码测试结果（不含注释部分）：

3.回答问题：

问题一：

　　（1）就实际类功能而言，publisher没有实际含义，就代码部分而言，由于析构函数和接口为纯虚函数而导致其为抽象类；

　　（2）不能；因为抽象类不能实例化；

问题二：

　　（1）void publish() const override; // 接口

　　　　void use() const override; // 接口；

　　（2）prototype for 'void Film::publish()'does not match any in class 'Film'；也就是没有该函数声明，因为在原类成员函数中，对应的函数是有const声明的。

问题三：

　　（1）Publisher 类型的指针；

　　（2）Book,Film,Music;

　　（3）防止产生内存泄漏，也就是在使用基类指针删除派生类对象时，能够让派生类对象资源释放；会造成内存泄漏，派生类对象没能释放对应的资源；

任务二：

1.源代码：

（1）book.hpp:

#pragma once
#include <string>

// 图书描述信息类Book: 声明
class Book {
public:
    Book(const std::string &name_, 
         const std::string &author_, 
         const std::string &translator_, 
         const std::string &isbn_, 
         double price_);

    friend std::ostream& operator<<(std::ostream &out, const Book &book);

private:
    std::string name;        // 书名
    std::string author;      // 作者
    std::string translator;  // 译者
    std::string isbn;        // isbn号
    double price;        // 定价
};

（2）book.cpp:

#include <iomanip>
#include <iostream>
#include <string>
#include "book.hpp"


// 图书描述信息类Book: 实现
Book::Book(const std::string &name_, 
          const std::string &author_, 
          const std::string &translator_, 
          const std::string &isbn_, 
          double price_):name{name_}, author{author_}, translator{translator_}, isbn{isbn_}, price{price_} {
}

// 运算符<<重载实现
std::ostream& operator<<(std::ostream &out, const Book &book) {
    using std::left;
    using std::setw;
    
    out << left;
    out << setw(15) << "书名:" << book.name << '\n'
        << setw(15) << "作者:" << book.author << '\n'
        << setw(15) << "译者:" << book.translator << '\n'
        << setw(15) << "ISBN:" << book.isbn << '\n'
        << setw(15) << "定价:" << book.price;

    return out;
}

（3）booksale.hpp:

#pragma once

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

// 图书销售记录类BookSales：声明
class BookSale {
public:
    BookSale(const Book &rb_, double sales_price_, int sales_amount_);
    int get_amount() const;   // 返回销售数量
    double get_revenue() const;   // 返回营收
    
    friend std::ostream& operator<<(std::ostream &out, const BookSale &item);

private:
    Book rb;         
    double sales_price;      // 售价
    int sales_amount;       // 销售数量
};

（4）booksale.cpp：

#include <iomanip>
#include <iostream>
#include <string>
#include "booksale.hpp"

// 图书销售记录类BookSales：实现
BookSale::BookSale(const Book &rb_, 
                   double sales_price_, 
                   int sales_amount_): rb{rb_}, sales_price{sales_price_}, sales_amount{sales_amount_} {
}

int BookSale::get_amount() const {
    return sales_amount;
}

double BookSale::get_revenue() const {
    return sales_amount * sales_price;
}

// 运算符<<重载实现
std::ostream& operator<<(std::ostream &out, const BookSale &item) {
    using std::left;
    using std::setw;
    
    out << left;
    out << item.rb << '\n'
        << setw(15) << "售价:" << item.sales_price << '\n'
        << setw(15) << "销售数量:" << item.sales_amount << '\n'
        << setw(15) << "营收:" << item.get_revenue();

    return out;
}

（5）task2.cpp:

#pragma once

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

// 图书销售记录类BookSales：声明
class BookSale {
public:
    BookSale(const Book &rb_, double sales_price_, int sales_amount_);
    int get_amount() const;   // 返回销售数量
    double get_revenue() const;   // 返回营收
    
    friend std::ostream& operator<<(std::ostream &out, const BookSale &item);

private:
    Book rb;         
    double sales_price;      // 售价
    int sales_amount;       // 销售数量
};

2.测试代码运行结果：

 3.回答问题：

问题一：

　　（1）两处；friend std::ostream& operator<<(std::ostream &out, const Book &book)此处用于Book类型；friend std::ostream& operator<<(std::ostream &out, const BookSale &item)用于BookSale类型；

　　（2）out << item.rb << '\n'；（输出Book对象）cout << record << '\n';（输出BookSale对象）；

问题二：

　　（1）使用算法库的sort函数，从迭代器的begin到end，通过函数compare_by_amount函数的逻辑去排序；

　　（2）sort(sales_records.begin(), sales_records.end(),[](const BookSale& a, const BookSale& b) {

　　　　　　return a.get_amount() < b.get_amount();});

任务三：

1.源代码：

（1）task3_1.cpp:

#include <iostream>

// 类A的定义
class A {
public:
    A(int x0, int y0);
    void display() const;

private:
    int x, y;
};

A::A(int x0, int y0): x{x0}, y{y0} {
}

void A::display() const {
    std::cout << x << ", " << y << '\n';
}

// 类B的定义
class B {
public:
    B(double x0, double y0);
    void display() const;

private:
    double x, y;
};

B::B(double x0, double y0): x{x0}, y{y0} {
}

void B::display() const {
    std::cout << x << ", " << y << '\n';
}

void test() {
    std::cout << "测试类A: " << '\n';
    A a(3, 4);
    a.display();

    std::cout << "\n测试类B: " << '\n';
    B b(3.2, 5.6);
    b.display();
}

int main() {
    test();
}

（2）task3_2:

#include <iostream>
#include <string>

// 定义类模板
template<typename T>
class X{
public:
    X(T x0, T y0);
    void display();

private:
    T x, y;
};

template<typename T>
X<T>::X(T x0, T y0): x{x0}, y{y0} {
}

template<typename T>
void X<T>::display() {
    std::cout << x << ", " << y << '\n';
}


void test() {
    std::cout << "测试1: 用int实例化类模板X" << '\n';
    X<int> x1(3, 4);
    x1.display();

    std::cout << "\n测试2:用double实例化类模板X" << '\n';
    X<double> x2(3.2, 5.6);
    x2.display();

    std::cout << "\n测试3: 用string实例化类模板X" << '\n';
    X<std::string> x3("hello", "oop");
    x3.display();
}

int main() {
    test();
}

2.测试代码运行结果：

（1）task3_1.cpp:

 （2）task3_2.cpp:

任务四：

（1）pet.hpp:

#pragma once
#include <string>
#include <iostream>
using namespace std;
class MachinePet {
public:
    MachinePet(const string& name = " ") {
        this->name = name;
    };
    virtual string get_nickname() const = 0;
    virtual string talk() const = 0;
    virtual ~MachinePet() = default;
protected:
    string name;
};

class PetCat : public MachinePet {
public:
    PetCat(const string& name = " ") {
        this->name = name;
    }
    string get_nickname() const override {
        return this->name;
    }
    string talk() const override {
        string a = "miao wu~";
        return a;
    }
    ~PetCat() = default;
private:
    string name;
};

class PetDog : public MachinePet {
public:
    PetDog(const string& name = " ") {
        this->name = name;
    }
    string get_nickname() const override {
        return this->name;
    }
    string talk() const override {
        string a = "wang wang~";
        return a;
    }
    ~PetDog() = default;
private:
    string name;
};

（2）task4.cpp:

#include <iostream>
#include <memory>
#include <vector>
#include "pet.hpp"

void test1() {
    std::vector<MachinePet*> pets;

    pets.push_back(new PetCat("miku"));
    pets.push_back(new PetDog("da huang"));

    for (MachinePet* ptr : pets) {
        std::cout << ptr->get_nickname() << " says " << ptr->talk() << '\n';
        delete ptr;  // 须手动释放资源
    }
}

void test2() {
    std::vector<std::unique_ptr<MachinePet>> pets;

    pets.push_back(std::make_unique<PetCat>("miku"));
    pets.push_back(std::make_unique<PetDog>("da huang"));

    for (auto const& ptr : pets)
        std::cout << ptr->get_nickname() << " says " << ptr->talk() << '\n';
}

void test3() {
    // MachinePet pet("little cutie");   // 编译报错：无法定义抽象类对象

    const PetCat cat("miku");
    std::cout << cat.get_nickname() << " says " << cat.talk() << '\n';

    const PetDog dog("da huang");
    std::cout << dog.get_nickname() << " says " << dog.talk() << '\n';
}

int main() {
    std::cout << "测试1: 使用原始指针\n";
    test1();

        std::cout << "\n测试2: 使用智能指针\n";
        test2();

    std::cout << "\n测试3: 直接使用类\n";
    test3();
}

2.测试代码运行结果：

 任务五：

1.源代码：

（1）Complex.hpp:

#pragma once
#include <iostream>

template<typename T>
class Complex {
public:
    Complex(T real_ = 0, T image_ = 0) {
        real = real_;
        image = image_;
    }
    Complex(const Complex& c) {
        real = c.real;
        image = c.image;
    }
    Complex& operator+= (const Complex<T>& c) {
        real += c.real;
        image += c.image;
        return *this;
    }
    double get_real() const {
        return real;
    }
    double get_imag() const {
        return image;
    }
    friend Complex operator+(const Complex<T>& a, const Complex<T>& b) {
        return Complex(a.real + b.real, a.image + b.image);
    }
    friend std::istream& operator >>(std::istream& in,Complex<T>& c) {
        in >> c.real >> c.image;
        return in;
    }
    friend std::ostream& operator <<(std::ostream& out,const Complex<T>& c) {
        if (c.image >= 0) {
            out << c.real << " + " << c.image << "i";
        }else
            out << c.real <<" - " << -c.image << "i";
        return out;
    }
    friend bool operator ==(const Complex<T>& a, const Complex<T>& b) {
        return ((a.real == b.real) && (a.image == b.image));
    }
    ~Complex() = default;
private:
    T real;
    T image;
};

（2）task5.cpp:

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

void test1() {
    using std::cout;
    using std::boolalpha;

    Complex<int> c1(2, -5), c2(c1);

    cout << "c1 = " << c1 << '\n';
    cout << "c2 = " << c2 << '\n';
    cout << "c1 + c2 = " << c1 + c2 << '\n';

    c1 += c2;
    cout << "c1 = " << c1 << '\n';
    cout << boolalpha << (c1 == c2) << '\n';
}

void test2() {
    using std::cin;
    using std::cout;

    Complex<double> c1, c2;
    cout << "Enter c1 and c2: ";
    cin >> c1 >> c2;
    cout << "c1 = " << c1 << '\n';
    cout << "c2 = " << c2 << '\n';

    const Complex<double> c3(c1);
    cout << "c3.real = " << c3.get_real() << '\n';
    cout << "c3.imag = " << c3.get_imag() << '\n';
}

int main() {
    std::cout << "自定义类模板Complex测试1: \n";
    test1();

    std::cout << "\n自定义类模板Complex测试2: \n";
    test2();
}

2.测试代码运行结果：

 实验总结：

（1）学会使用operator去重载运算符，其中，特别注意const的对应，在istream中，对操作对象不能加上const;

（2）灵活使用模板函数方式，可以实现泛化类型，以减少多余重复代码的产生，使代码更加简洁；

（3）合理运用智能指针可以减少对于泄漏内存的疏忽，使得代码更加安全，也可以让程序员更加注重业务逻辑，提高了开发效率；