OOP-实验5
实验任务1
源代码
publish.hpp
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#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
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#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
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#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
实验结论
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。
答：Publisher 类包含纯虚函数。具体依据是：在 publisher.hpp 中，Publisher 类声明了纯虚函数 virtual void publish() const = 0; 和 virtual void use() const = 0;
（2）如果在 main.cpp 里直接写 Publisher p; 能否编译通过？为什么？
答：不能编译通过。因为 Publisher 是抽象类（包含纯虚函数），抽象类不能被直接实例化，只能通过派生类实例化对象。
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。
答： virtual void publish() const = 0; 和 virtual void use() const = 0;
（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？
答：基类 Publisher 中的纯虚函数是 const 成员函数，派生类 Film 中重写的函数签名必须完全一致（包括 const 修饰符）。
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？
答：Publisher *，基类指针。
（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）
答：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？
答：基类 Publisher 的析构函数声明为 virtual 是为了支持多态析构。当通过基类指针删除派生类对象时，虚析构函数确保调用正确的派生类析构函数，从而正确释放整个对象的所有资源。若删除，则会导致内存泄漏。
实验任务二
源代码
book.hpp
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#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
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#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
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#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
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#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
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#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();
}
运行结果
实验结论
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？
答：2处。Book类型和BookSale类型。
（2）找出使用重载<<输出对象的代码，写在下面。
答：cout << record << '\n';。
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？
答：定义比较函数后使用库函数sort（）；
（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"？
答：
sort(sales_records.begin(), sales_records.end(),
[](const BookSale &x1, const BookSale &x2) {
return x1.get_amount() > x2.get_amount();
});
实验任务三
源代码
task3_1.cpp
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#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();
}
task3_2.cpp
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#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();
}
运行结果
实验结论
- 类模板用 template
把“类型”抽象成参数，一份代码可生成多个具体类。 - 在类外实现成员函数时，必须加模板头并写完整类名
X<T>。 - 使用时要先“实例化”：
X<int> x1(3,4);，编译器据此生成真正的类。 - 实例化类型必须支持模板内所有操作（如 <<），否则编译报错。
- 理解类模板后，再看标准库用法——complex
、vector ——只是现成模板的实例化而已。
实验任务四
源代码
pet.hpp
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#include <iostream>
using namespace std;
class MachinePet {
protected:
string nickname;
public:
MachinePet(const string &name) : nickname(name) {}
virtual ~MachinePet() = default;
string get_nickname() const {
return nickname;
}
virtual string talk() const = 0;
};
class PetCat : public MachinePet {
public:
PetCat(const string &name) : MachinePet(name) {}
string talk() const override {
return "Meow";
}
};
class PetDog : public MachinePet {
public:
PetDog(const string &name) : MachinePet(name) {}
string talk() const override {
return "Woof";
}
};
task4.cpp
点击查看代码
#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();
}
运行结果
实验任务五
源代码
Complex.hpp
点击查看代码
#include <iostream>
template <typename T>
class Complex {
private:
T real;
T imag;
public:
Complex(T r = 0, T i = 0);
Complex(const Complex& other) : real(other.real), imag(other.imag) {}
T get_real() const { return real; }
T get_imag() const { return imag; }
Complex operator+(const Complex& other) const;
Complex& operator+=(const Complex& other);
bool operator==(const Complex& other) const;
template <typename U>
friend std::ostream& operator<< (std::ostream& os, const Complex<U>& c);
template <typename U>
friend std::istream& operator>> (std::istream& is, Complex<U>& c);
};
template <typename T>
Complex<T>::Complex(T r, T i) : real(r), imag(i) {}
template <typename T>
Complex<T> Complex<T>::operator+(const Complex& other) const {
return Complex(real + other.real, imag + other.imag);
}
template <typename T>
Complex<T>& Complex<T>::operator+=(const Complex& other) {
real += other.real;
imag += other.imag;
return *this;
}
template <typename T>
bool Complex<T>::operator==(const Complex& other) const {
return (real == other.real) && (imag == other.imag);
}
template <typename T>
std::ostream& operator<<(std::ostream& os, const Complex<T>& c) {
if (c.imag < 0) {
os << c.real << " - " << -c.imag << "i";
} else {
os << c.real << " + " << c.imag << "i";
}
return os;
}
template <typename T>
std::istream& operator>>(std::istream& is, Complex<T>& c) {
is >> c.real >> c.imag ;
return is;
}
task5.cpp
点击查看代码
#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
实验总结
- 了解掌握了抽象类和纯虚函数的关系，知道了纯抽象类不可实例化
- 熟悉掌握了模板类的定义和使用，在类外使用类时要使用
X<int>的形式 - 为了防止内存泄漏，要在基类使用虚析构函数
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