实验5
实验5
实验结论:
实验任务1:
源码:
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();
}
运行测试截图:
回答问题:
问题1：
（1）是什么决定了 Publisher 是抽象类？用一句话说明，并指出代码中的具体依据。
因为它包含纯虚函数。依据：在 publisher.hpp 里有形如 virtual void publish() const = 0; 的声明。
（2）如果在 main.cpp 里直接写 Publisher p; 能否编译通过？为什么？
不能编译通过。因为抽象类不能实例化（含有纯虚函数）。
问题2：
（1）Book 、 Film 、 Music 必须实现哪两个函数才能通过编译？请写出其完整函数声明。
void publish() const; 和 void info() const;
void publish() const override;
void info() const override;
（2）在 publisher.cpp 的 Film 类实现中，把两个成员函数实现里的 const 去掉（保持函数体不变），重新编译，报错信息是什么？
问题3：
（1）在 test1() 里， for (Publisher *ptr : v) 中 ptr 的声明类型是什么？
Publisher*
（2）当循环执行到 ptr->publish(); 时， ptr 实际指向的对象类型分别有哪些？（按循环顺序写出）
Book、Film、Music。
（3）基类 Publisher 的析构函数为何声明为 virtual ？若删除 virtual ，执行 delete ptr; 会出现什么问题？
基类析构函数声明为 virtual 是为了多态删除，确保 delete ptr; 时能调用派生类析构函数。若无 virtual，delete 只调用基类析构，导致资源泄漏。
实验任务2:
源码:
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
};
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;
}
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
};
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;
}
task2.cpp
#include <algorithm>
#include <iomanip>
#include <iostream>
#include <string>
#include <vector>
#include "booksale.hpp"
// 按图书销售数量比较
bool compare_by_amount(const BookSale &x1, const BookSale &x2)
{
return x1.get_amount() > x2.get_amount();
}
void test()
{
using std::cin;
using std::cout;
using std::getline;
using std::sort;
using std::string;
using std::vector;
using std::ws;
vector<BookSale> sales_records; // 图书销售记录表
int books_number;
cout << "录入图书数量: ";
cin >> books_number;
cout << "录入图书销售记录\n";
for (int i = 0; i < books_number; ++i)
{
string name, author, translator, isbn;
double price;
cout << string(20, '-') << "第" << i + 1 << "本图书信息录入" << string(20, '-') << '\n';
cout << "录入书名: ";
getline(cin >> ws, name);
cout << "录入作者: ";
getline(cin >> ws, author);
cout << "录入译者: ";
getline(cin >> ws, translator);
cout << "录入isbn: ";
getline(cin >> ws, isbn);
cout << "录入定价: ";
cin >> price;
Book book(name, author, translator, isbn, price);
double 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_records.push_back(record);
}
// 按销售册数排序
sort(sales_records.begin(), sales_records.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, '=') << '\n';
for (auto &record : sales_records)
{
cout << record << '\n';
cout << string(40, '-') << '\n';
}
}
int main()
{
test();
}
运行测试截图:
回答问题:
问题1：
（1）找出运算符 << 被重载了几处？分别用于什么类型？
2处，分别用于 Book 和 BookSale 类型。
（2）找出使用重载 << 输出对象的代码，写在下面。
cout << book;
cout << sale;
问题2：
（1）图书销售记录"按销售数量降序排序"，代码是如何实现的？
通过自定义比较函数（如 compareBySaleCount），用 sort(v.begin(), v.end(), compareBySaleCount); 实现降序排序。
（2）拓展（选答*）：如果使用lambda表达式，如何实现"按销售数量降序排序"？
sort(v.begin(), v.end(), [](const BookSale &a, const BookSale &b) { return a.getCount() > b.getCount(); });
实验任务4:
源码:
Pet.hpp
#ifndef PET_HPP
#define PET_HPP
#include <string>
// 抽象基类：机器宠物
class MachinePet
{
private:
std::string nickname; // 宠物昵称
public:
// 初始化昵称
MachinePet(const std::string &name) : nickname(name) {}
// 获取昵称
const std::string &get_nickname() const
{
return nickname;
}
// 纯虚函数：宠物叫声
virtual std::string talk() const = 0;
// 虚析构函数
virtual ~MachinePet() = default;
};
// 派生类：机器猫
class PetCat : public MachinePet
{
public:
// 调用父类构造初始化昵称
PetCat(const std::string &name) : MachinePet(name) {}
// 实现猫的叫声
std::string talk() const override
{
return "Meow~";
}
};
// 派生类：机器狗
class PetDog : public MachinePet
{
public:
// 调用父类构造初始化昵称
PetDog(const std::string &name) : MachinePet(name) {}
// 实现狗的叫声
std::string talk() const override
{
return "Woof~";
}
};
#endif // PET_HPP
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();
}
运行测试截图:
实验任务5:
源码:
Complex.hpp
#ifndef COMPLEX_HPP
#define COMPLEX_HPP
#include <iostream>
// 复数类模板
template <typename T>
class Complex
{
private:
T real_; // 实部
T imag_; // 虚部
public:
Complex() : real_(0), imag_(0) {}
Complex(T real, T imag) : real_(real), imag_(imag) {}
Complex(const Complex<T> &other) : real_(other.real_), imag_(other.imag_) {}
// 获取实部
T get_real() const
{
return real_;
}
// 获取虚部
T get_imag() const
{
return imag_;
}
// 4. 重载 += 运算符
Complex<T> &operator+=(const Complex<T> &other)
{
this->real_ += other.real_;
this->imag_ += other.imag_;
return *this;
}
// 5. 重载 == 运算符
bool operator==(const Complex<T> &other) const
{
return (this->real_ == other.real_) && (this->imag_ == other.imag_);
}
// 声明友元：重载 << 输出运算符
template <typename U>
friend std::ostream &operator<<(std::ostream &os, const Complex<U> &c);
// 声明友元：重载 >> 输入运算符
template <typename U>
friend std::istream &operator>>(std::istream &is, Complex<U> &c);
};
// 6. 重载 + 运算符
template <typename T>
Complex<T> operator+(const Complex<T> &c1, const Complex<T> &c2)
{
// 复用 += 逻辑，避免代码冗余
Complex<T> res = c1;
res += c2;
return res;
}
// 7. 重载 << 输出运算符
template <typename T>
std::ostream &operator<<(std::ostream &os, const Complex<T> &c)
{
os << c.real_;
if (c.imag_ >= 0)
{
os << " + " << c.imag_ << "i";
}
else
{
os << " - " << -c.imag_ << "i";
}
return os;
}
// 8. 重载 >> 输入运算符
template <typename T>
std::istream &operator>>(std::istream &is, Complex<T> &c)
{
is >> c.real_ >> c.imag_;
return is;
}
#endif // COMPLEX_HPP
task5.cpp
#include <iostream>
#include "Complex.hpp"
void test1()
{
using std::boolalpha;
using std::cout;
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();
}
运行测试截图:
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