实验5
Task1
源代码
Publisher.h
#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.h"
// 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.h"
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();
}
运行截图
问题
问题1：抽象类机制
（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。
（2）如果在 main.cpp 里直接写 Publisher p; 能否编译通过？为什么？
（1）Publisher类中含有纯虚函数
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
（2）不能。Publisher是纯虚函数，不能实例化
问题2：纯虚函数与接口继承
（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。
（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？
（1）实现基类中的纯虚函数
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
（2）
问题3：运行时多态与虚析构
（1）在 test1() 里， for (Publisher *ptr : v) 中 ptr 的声明类型是什么？
（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）
（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？
（1）Publisher*
（2）Book Film Music
（3）在派生类的析构函数起作用时，确保能够正确调用相应的析构函数
不能正确调用相应的析构函数来释放资源，可能会导致内存泄露
Task2
源代码
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();
}
运行截图
问题
问题1：重载运算符<<
（1）找出运算符 << 被重载了几处？分别用于什么类型？
（2）找出使用重载 << 输出对象的代码，写在下面。
（1）两次
第一次，Book.h文件中：
friend std::ostream& operator<<(std::ostream& out, const Book& book);
用于Book类
第二次，BookSale.h文件中：
friend std::ostream& operator<<(std::ostream& out, const BookSale& item);
用于BookSale类
（2）cout << t << endl;
问题2：图书销售统计
（1）图书销售记录"按销售数量降序排序"，代码是如何实现的？
（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"？
（1）通过sort(sales_lst.begin(), sales_lst.end(), compare_by_amount);语句
从sales_lst.begin()到sales_lst.end()，依次调用compare_by_amount()函数
Task4
源代码
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();
}
运行截图
Task5
源代码
Complex.h
#pragma once
#include <iostream>
#include <cmath>
template<typename T>
class Complex{
public:
Complex(T real_ = 0, T imag_ = 0);
Complex(const Complex<T>& other);
T get_real() const;
T get_imag() const;
Complex<T>& operator+=(const Complex<T>& other) {
real += other.real;
imag += other.imag;
return *this;
}
Complex<T> operator+(const Complex<T>& other) const {
Complex<T> temp = *this;
temp += other;
return temp;
}
bool operator==(const Complex<T>& other) const {
return (real == other.real) && (imag == other.imag);
}
// 声明友元：让全局<<能访问私有成员
friend std::ostream& operator<<(std::ostream& out, const Complex<T>& c) {
out << c.real
<< (c.imag >= 0 ? " + " : " - ")
<< std::abs(c.imag) << "i"; // 用abs避免负负得正
return out;
}
// 声明友元：让全局>>能访问私有成员
friend std::istream& operator>>(std::istream& in, Complex<T>& c) {
in >> c.real >> c.imag;
return in;
}
private:
T real, imag;
};
template<typename T>
Complex<T>::Complex(T real_, T imag_) :real{ real_ }, imag{ imag_ } {}
template<typename T>
Complex<T>::Complex(const Complex<T>& other)
: real(other.real), imag(other.imag) {
}
template<typename T>
T Complex<T>::get_imag() const {
return imag;
}
template<typename T>
T Complex<T>::get_real() const {
return real;
}
task5
#pragma once
#include <iostream>
#include <cmath>
template<typename T>
class Complex{
public:
Complex(T real_ = 0, T imag_ = 0);
Complex(const Complex<T>& other);
T get_real() const;
T get_imag() const;
Complex<T>& operator+=(const Complex<T>& other) {
real += other.real;
imag += other.imag;
return *this;
}
Complex<T> operator+(const Complex<T>& other) const {
Complex<T> temp = *this;
temp += other;
return temp;
}
bool operator==(const Complex<T>& other) const {
return (real == other.real) && (imag == other.imag);
}
// 声明友元：让全局<<能访问私有成员
friend std::ostream& operator<<(std::ostream& out, const Complex<T>& c) {
out << c.real
<< (c.imag >= 0 ? " + " : " - ")
<< std::abs(c.imag) << "i"; // 用abs避免负负得正
return out;
}
// 声明友元：让全局>>能访问私有成员
friend std::istream& operator>>(std::istream& in, Complex<T>& c) {
in >> c.real >> c.imag;
return in;
}
private:
T real, imag;
};
template<typename T>
Complex<T>::Complex(T real_, T imag_) :real{ real_ }, imag{ imag_ } {}
template<typename T>
Complex<T>::Complex(const Complex<T>& other)
: real(other.real), imag(other.imag) {
}
template<typename T>
T Complex<T>::get_imag() const {
return imag;
}
template<typename T>
T Complex<T>::get_real() const {
return real;
}
运行截图
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