OOP5

任务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
};

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';
}

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();
}

运行结果

问题

一：（1）publisher中含有纯虚函数

（2）在main中直接写会报错，因为抽象类不允许实例化

二：（1）void publish() const override      void use() const override

（2）报错信息为声明与 "void Film::publish() const" (已声明 所在行数:38，所属文件:"*\publisher.hpp") 不兼容C/C++(147)

三：（1）Publisher*

（2）Book Film Music

（3）如果析构函数不是虚函数则基类对象正常释放，派生类无法释放

任务2

Book.h

#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
};

BookSale.h

#pragma once
#include <string>
#include "Book.h"
// 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
};

Book.cpp

#include <iomanip>
#include <iostream>
#include <string>
#include "Book.h"
// 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;
}

BookSale.cpp

#include <iomanip>
#include <iostream>
#include <string>
 
#include "BookSale.h"
 
// 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;
}

task2.cpp

#include "BookSale.h"
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
// 按图书销售数额比较
bool compare_by_amount(const BookSale& x1, const BookSale& x2) {
    return x1.get_amount() > x2.get_amount();
}
void test() {
    using namespace std;
    vector<BookSale> sales_lst; // 存放图书销售记录
    int books_number;
    cout << "录入图书数量: ";
    cin >> books_number;
    cout << "录入图书销售记录" << endl;
    for (int i = 0; i < books_number; ++i) {
        string name, author, translator, isbn;
        float price;
        cout << string(20, '-') << "第" << i + 1 << "本图书信息录入" << string(20, '-') <<
            endl;
        cout << "录入书名: "; cin >> name;
        cout << "录入作者: "; cin >> author;
        cout << "录入译者: "; cin >> translator;
        cout << "录入isbn: "; cin >> isbn;
        cout << "录入定价: "; cin >> price;
        Book book(name, author, translator, isbn, price);
        float sales_price;
        int sales_amount;
        cout << "录入售价: "; cin >> sales_price;
        cout << "录入销售数量: "; cin >> sales_amount;
        BookSale record(book, sales_price, sales_amount);
        sales_lst.push_back(record);
    }
    // 按销售册数排序
    sort(sales_lst.begin(), sales_lst.end(), compare_by_amount);
    // 按销售册数降序输出图书销售信息
    cout << string(20, '=') << "图书销售统计" << string(20, '=') << endl;
    for (auto& t : sales_lst) {
        cout << t << endl;
        cout << string(40, '-') << endl;
    }
}
int main() {
    test();
}

运行结果

问题

一：（1）两处；用于Book类型和BookSale类型

（2）cout << record << '\n'

二：使用了一个布尔函数bool compare_by_amount 比较大小，作为sort的比较逻辑，使用lambda表达式只需要把第三个参数改为： [](const BookSale& x1, const BookSale& x2)

任务4

Pet.h

#pragma once
 
#include <iostream>
#include <string> 
 
class MachinePet
{
public:
    std::string get_nickname() const;
    virtual std::string talk() const = 0;
 
    MachinePet(std::string name_);
    virtual ~MachinePet() = 0; 
private:
    std::string nickname;
};
 
class PetCat : public MachinePet {
public:
    std::string talk() const override;
    PetCat(std::string name_);
};
 
class PetDog : public MachinePet {
public:
    std::string talk() const override;
    PetDog(std::string name_) : MachinePet(name_) {}
};

Pet.cpp

#include "Pet.h"
 
std::string MachinePet::get_nickname() const {
    return nickname;
}
 
MachinePet::MachinePet(std::string name_) : nickname{ name_ } {}
 
MachinePet::~MachinePet() {}
 
std::string PetCat::talk() const {
    return "miao wu~";
}
 
PetCat::PetCat(std::string name_) : MachinePet(name_) {}
 
std::string PetDog::talk() const {
    return "wang wang~";
}

task4.cpp

#include <iostream>
#include <memory>
#include <vector>
#include "Pet.h"
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();
}

运行结果

任务5

Complex.h

#include<iostream>
#include<string>

template<typename T>
class Complex {
private:
    T real;
    T imag;
public:
    Complex(T r, T i) : real(r), imag(i) {}
    Complex() : real(0), imag(0) {}

    friend std::ostream& operator<<(std::ostream &os, const Complex<T> &c) {
        os << c.real << (c.imag >= 0 ? "+" : "") << c.imag << "i";
        return os;
    }
    friend std::istream& operator>>(std::istream &is, Complex<T> &c) {
        char sign, i_char;
        is >> c.real >> sign >> c.imag >> i_char;
        if (sign == '-') {
            c.imag = -c.imag;
        }
        return is;
    }

    friend Complex<T> operator+(const Complex<T> &a, const Complex<T> &b) {
        return Complex<T>(a.real + b.real, a.imag + b.imag);
    }

    friend Complex<T>& operator+=(Complex<T> &lhs, const Complex<T> &rhs) {
        lhs.real += rhs.real;
        lhs.imag += rhs.imag;
        return lhs;
    }

    friend bool operator==(const Complex<T> &lhs, const Complex<T> &rhs) {
        return lhs.real == rhs.real && lhs.imag == rhs.imag;
    }

    T get_real() const {
        return real;
    }

    T get_imag() const {
        return imag;
    }


};

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();
}

运行结果