实验5 多态
实验任务1
实验代码：
publisher.hpp:
#pragma once
#include <string>
class Publisher {
public:
Publisher(const std::string& name_ = "");
virtual ~Publisher() = default;
public:
virtual void publish() const = 0;
virtual void use() const = 0;
protected:
std::string name;
};
class Book : public Publisher {
public:
Book(const std::string& name_ = "", const std::string& author_ = "");
public:
void publish() const override;
void use() const override;
private:
std::string author;
};
class Film : public Publisher {
public:
Film(const std::string& name_ = "", const std::string& director_ = "");
public:
void publish() const override;
void use() const override;
private:
std::string director;
};
class Music : public Publisher {
public:
Music(const std::string& name_ = "", const std::string& artist_ = "");
public:
void publish() const override;
void use() const override;
private:
std::string artist;
};
publisher.cpp:
#include <iostream>
#include <string>
#include "publisher.hpp"
Publisher::Publisher(const std::string& name_) : name{ name_ } {
}
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::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::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:
#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）Publisher中包含纯虚函数，因此它是抽象类
依据：
virtual void publish() const = 0;
virtual void use() const = 0;
（2）不能编译通过，抽象类不能直接实例化对象，只能作为基类被继承
问题2：
（1）publisher函数，use函数
void publish() const override;
void use() const override;
(2)
问题3：
(1) ptr的声明类型是Publisher*
(2) 实际指向的类型是Book,Film,Music
(3) 确保通过基类指针删除子类对象时，能正确调用子类的析构函数
删除virtual后，执行delete ptr，仅调用基类Publisher的析构函数，子类的析构函数不会调用，导致内存泄漏
实验任务2
实验代码：
book.hpp:
#pragma once
#include <string>
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;
std::string author;
std::string translator;
std::string isbn;
double price;
};
book.cpp:
#include <iomanip>
#include <iostream>
#include <string>
#include "book.hpp"
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_ } {
}
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"
class BookSale {
public:
BookSale(const Book& rb_, double sales_price_, int sales_amount_);
int get_amount() const;
double get_revenue() const;
friend std::ostream& operator<<(std::ostream& out, const BookSale& item);
private:
Book rb;
double sales_price;
int sales_amount;
};
booksale.cpp:
#include <iomanip>
#include <iostream>
#include <string>
#include "booksale.hpp"
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;
}
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.hpp"
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
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;
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);
}
sort(sales_lst.begin(), sales_lst.end(), compare_by_amount);
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();
}
运行测试截图：
回答问题：
问题1：
（1）代码中重载了2次 << 运算符
第一次：在 book.cpp 中，重载 std::ostream& operator<<(std::ostream &out, const Book &book) ，用于输出 Book 类对象
第二次：在 booksale.cpp 中，重载 std::ostream& operator<<(std::ostream &out, const BookSale &item) ，用于输出 BookSale 类对象
（2）
cout << string(20, '=') << "图书销售统计" << string(20, '=') << endl;
for (auto& t : sales_lst) {
cout << t << endl;
cout << string(40, '-') << endl;
}
问题2：
（1）代码中通过自定义比较函数 compare_by_amount 和 sort 算法实现：
销售数量大的排前面
bool compare_by_amount(const BookSale &x1, const BookSale &x2) {
return x1.get_amount() > x2.get_amount();
}
再调用 sort 函数对 sales_list 排序
sort(sales_list.begin(), sales_list.end(), compare_by_amount);
实验任务4
实验代码：
pet.hpp:
#pragma once
#include<iostream>
#include<string>
class MachinePet {
public:
MachinePet(const std::string& name_ = "") :nickname{ name_ } {};
virtual ~MachinePet() = default;
virtual std::string get_nickname() const {
return nickname;
}
virtual std::string talk() const = 0;
private:
std::string nickname;
};
class PetCat : public MachinePet {
public:
PetCat(const std::string& name_ = "") :MachinePet{ name_ } {};
std::string talk() const override {
return "mi mi mi mi mi";
}
};
class PetDog : public MachinePet {
public:
PetDog(const std::string& name_ = "") :MachinePet{ name_ } {};
std::string talk() const override {
return "ga ga ga ga ga";
}
};
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;
}
}
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() {
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：
实验代码：
Complex.hpp:
#pragma once
#include <iostream>
#include <string>
template<typename T>
class Complex {
public:
Complex() : real{ 0 }, imag{ 0 } {};
Complex(T a, T b) : real{ a }, imag{ b } {};
Complex(const Complex<T>& other) : real{ other.real }, imag{ other.imag } {};
T get_real() const { return real; };
T get_imag() const { return imag; };
template<typename U>
friend std::ostream& operator<<(std::ostream& out, const Complex<U>& C);
template<typename U>
friend std::istream& operator>>(std::istream& in, Complex<U>& C);
friend Complex<T> operator+(const Complex<T>& c1, const Complex<T>& c2) {
return Complex<T>(c1.real + c2.real, c1.imag + c2.imag);
}
Complex<T>& operator+=(const Complex<T>& C);
bool operator==(const Complex<T>& C) const;
private:
T real, imag;
};
template<typename T>
std::ostream& operator<<(std::ostream& out, const Complex<T>& C) {
if (C.imag >= 0)
out << C.real << '+' << C.imag << 'i';
else
out << C.real << C.imag << 'i';
return out;
}
template<typename T>
std::istream& operator>>(std::istream& in, Complex<T>& C) {
in >> C.real >> C.imag;
return in;
}
template<typename T>
Complex<T>& Complex<T>::operator+=(const Complex<T>& C) {
real += C.real;
imag += C.imag;
return *this;
}
template<typename T>
bool Complex<T>::operator==(const Complex<T>& C) const {
return (real == C.real) && (imag == C.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();
}
运行测试截图：
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