实验5 继承和多态

一、实验目的

正确使用C++语法重载运算符，理解编译器是如何将表达式转换为对运算符重载的调用的

基于问题场景，合理使用派生机制，虚函数，纯虚函数，抽象类，实现接口继承与运行时多态

能灵活应用类的组合继承，多态编程解决实际问题

二、实验准备

第7章类的继承

第8章多态

9.1节类模板

三、实验内容

3. 实验任务3

代码：

hpp文件：

 1 #ifndef PETS_HPP
 2 #define PETS_HPP
 3 #include <string>
 4 using namespace std;
 5 
 6 
 7 class MachinePets{
 8     private:
 9         string nickname;
10     public:
11         MachinePets(const string &s);
12         string get_nickname() const { return nickname; }
13         virtual string talk()=0 ;
14     
15          
16          virtual ~MachinePets() = default;  // 添加虚析构函数
17         
18 };
19 // MachinePets构造函数实现
20 MachinePets::MachinePets(const string &s) : nickname(s) {}
21 
22 
23 class PetCats:public MachinePets{
24     public:
25         PetCats(const string &s);
26         string talk() override; 
27 };
28 // PetCats构造函数实现
29 PetCats::PetCats(const string &s) : MachinePets(s) {}
30 string PetCats::talk() {
31     return "miao wu~";
32 }
33 
34 class PetDogs:public MachinePets {
35 public:
36     PetDogs(const string &s);  
37     string talk() override;  
38 };
39 
40 
41 // PetDogs构造函数实现
42 PetDogs::PetDogs(const string &s) : MachinePets(s) {}
43 string PetDogs::talk() {
44     return "wang wang~";
45 }
46 
47 #endif

task文件：

 1 #include <iostream>
 2 #include <vector>
 3 #include "petts.hpp"
 4 
 5 void test() {
 6     using namespace std;
 7 
 8     vector<MachinePets *> pets;
 9 
10     pets.push_back(new PetCats("miku"));
11     pets.push_back(new PetDogs("da huang"));
12 
13     for(auto &ptr: pets)
14         cout <<ptr->get_nickname() << " says " << ptr->talk() << endl;
15 }
16 
17 int main() {
18     test();
19 }

运行截图：

4. 实验任务4

代码：

头文件：

 1 #ifndef FILM_HPP
 2 #define FILM_HPP
 3 
 4 #include <iostream>
 5 #include <string>
 6 
 7 class Film {
 8 private:
 9     std::string filmname;
10     std::string director;
11     std::string area;
12     int year;
13 
14 public:
15     // 默认构造函数
16     Film() = default;
17 
18     // 带参数的构造函数
19     Film(const std::string& name, const std::string& dir, const std::string& area, int year)
20         : filmname(name), director(dir), area(area), year(year) {}
21 
22     // 输入流重载
23     friend std::istream& operator>>(std::istream& is, Film& f);
24 
25     // 输出流重载
26     friend std::ostream& operator<<(std::ostream& os, const Film& f);
27 
28     // 获取年份用于比较
29     int getYear() const { return year; }
30 };
31 
32 // 输入流重载实现
33 std::istream& operator>>(std::istream& is, Film& f) {
34     std::cout << "录入片名：";
35     is >> f.filmname;
36     std::cout << "录入导演：";
37     is >> f.director;
38     std::cout << "录入制片国家/地区：";
39     is >> f.area;
40     std::cout << "录入上映年份：";
41     is >> f.year; // 读取年份
42     return is;
43 }
44 
45 // 输出流重载实现
46 std::ostream& operator<<(std::ostream& os, const Film& f) {
47     os << f.filmname << "\t" << f.director << "\t" << f.area << "\t" << f.year;
48     return os;
49 }
50 
51 #endif
52 
53

task文件：

 1 #include "petts.hpp"
 2 #include <iostream>
 3 #include <string>
 4 #include <vector>
 5 #include <algorithm>
 6 //增加这一部分 
 7 bool compare_by_year(const Film& f1, const Film& f2) {
 8     return f1.getYear() < f2.getYear(); // 按年份升序比较
 9 }
10 
11 void test() {
12     using namespace std;
13     
14     int n;
15     cout << "输入电影数目: ";
16     cin >> n;
17 
18     cout << "录入" << n << "部影片信息" << endl;
19     vector<Film> film_lst;
20     for(int i = 0; i < n; ++i) {
21         Film f;
22         cout << string(20, '-') << "第" << i+1 << "部影片录入" << string(20, '-') << endl;
23         cin >> f;
24         film_lst.push_back(f);
25     }
26 
27     // 按发行年份升序排序
28     sort(film_lst.begin(), film_lst.end(), compare_by_year);
29 
30     cout << string(20, '=') + "电影信息(按发行年份)" +  string(20, '=')<< endl;
31     for(auto &f: film_lst)
32         cout << f << endl;
33 }
34 
35 int main() {
36     test();
37 }

运行截图：（换一组）

5. 实验任务5

代码：

头文件：

 1 #ifndef COMPLEX_HPP
 2 #define COMPLEX_HPP
 3 
 4 #include <iostream>
 5 #include <string>
 6 
 7 using namespace std;
 8 template <typename T>
 9  
10 class Complex {
11 private:
12     T real;
13     T imag;
14 public:
15     Complex():real(T()),imag(T()){
16     }//默认构造函数
17     
18     //有参构造函数
19     Complex(T r,T i):real(r),imag(i){
20     } 
21     T get_real() const {return real ;}
22     
23     T get_imag() const{return imag;}    
24     
25     
26     Complex<T>& operator += (const Complex <T> & other){
27         real+=other.real;
28         imag+=other.imag;
29         return *this;
30     }
31     bool operator ==(const Complex <T>& other )const{
32     return (real==other.real)&&(imag==other.imag);}
33     
34     Complex<T> operator +(const Complex<T>& other)const{
35     return Complex<T>(real+other.real,imag+other.imag);}
36     
37     friend istream& operator>>(istream& is,Complex<T> &c){
38      T r, i;
39         is >> r >> i; // 读取实部和虚部
40         c.real = r;
41         c.imag = i;
42         return is;
43     }
44     friend ostream& operator <<(ostream& os,const Complex<T>&c){
45         os<<c.real;
46         if(c.imag>=0){
47             os<<"+";
48             
49         }
50         os<<c.imag<<"i";
51         return os;
52     }
53     };
54     
55 
56 #endif
57 
58

task文件：

 1 #include "petts.hpp"
 2 #include <iostream>
 3 
 4 using std::cin;
 5 using std::cout;
 6 using std::endl;
 7 using std::boolalpha;
 8 
 9 void test1() {
10     Complex<int> c1(2, -5), c2(c1);
11 
12     cout << "c1 = " << c1 << endl;
13     cout << "c2 = " << c2 << endl;
14     cout << "c1 + c2 = " << c1 + c2 << endl;
15     
16     c1 += c2;
17     cout << "c1 = " << c1 << endl;
18     cout << boolalpha << (c1 == c2) << endl;
19 }
20 
21 void test2() {
22     Complex<double> c1, c2;
23     cout << "Enter c1 and c2: ";
24     cin >> c1 >> c2;
25     cout << "c1 = " << c1 << endl;
26     cout << "c2 = " << c2 << endl;
27 
28     cout << "c1.real = " << c1.get_real() << endl;
29     cout << "c1.imag = " << c1.get_imag() << endl;
30 }
31 
32 int main() {
33     cout << "自定义类模板Complex测试1: " << endl;
34     test1();
35 
36     cout << endl;
37 
38     cout << "自定义类模板Complex测试2: " << endl;
39     test2();
40 }

运行截图：（换一组）

6. 实验任务6

代码：

date.h,

 1 #pragma once
 2 
 3 class Date {
 4 private:
 5     int year;
 6     int month;
 7     int day;
 8     int totalDays;
 9 
10 public:
11     Date(int year, int month, int day);
12 
13     int getYear() const { return year; }
14     int getMonth() const { return month; }
15     int getDay() const { return day; }
16     int getMaxDay() const;
17 
18     bool isLeapYear() const {
19         return year % 4 == 0 && year % 100 != 0 || year % 400 == 0;
20     }
21     void show() const;
22 
23     int operator-(const Date& date) const {
24         return totalDays - date.totalDays;
25     }
26 };

date.cpp,

 1 #include "date.h"
 2 #include <iostream>
 3 #include <cstdlib>
 4 
 5 using namespace std;
 6 
 7 namespace {
 8     const int DAYS_BEFORE_MONTH[] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 };
 9 }
10 
11 Date::Date(int year, int month, int day) : year(year), month(month), day(day) {
12     if (day <= 0 || day > getMaxDay()) {
13         cout << "Invalid date: ";
14         show();
15         cout << endl;
16         exit(1);
17     }
18     int years = year - 1;
19     totalDays = years * 365 + years / 4 - years / 100 + years / 400 + DAYS_BEFORE_MONTH[month - 1] + day;
20     if (isLeapYear() && month > 2) totalDays++;
21 }
22 
23 int Date::getMaxDay() const {
24     if (isLeapYear() && month == 2)
25         return 29;
26 
27     else return DAYS_BEFORE_MONTH[month] - DAYS_BEFORE_MONTH[month - 1];
28 }
29 
30 void Date::show() const {
31     cout << getYear() << "-" << getMonth() << "-" << getDay();
32 }

accumulator.h,

 1 #pragma once
 2 #include "date.h"
 3 
 4 class Accumulator {
 5 private:
 6     Date lastDate;
 7     double value;
 8     double sum;
 9 
10 public:
11     Accumulator(const Date& date, double value) : lastDate(date), value(value), sum{ 0 } {}
12 
13     double getSum(const Date& date) const {
14         return sum + value * (date - lastDate);
15     }
16 
17     void change(const Date& date, double value) {
18         sum = getSum(date);
19         lastDate = date;
20         this->value = value;
21     }
22 
23     void reset(const Date& date, double value) {
24         lastDate = date;
25         this->value = value;
26         sum = 0;
27     }
28 };

account.h,

 1 #pragma once
 2 
 3 #include "date.h"
 4 #include "accumulator.h"
 5 #include <string>
 6 
 7 using namespace std;
 8 
 9 class Account {
10 private:
11     string id;
12     double balance;
13     static double total;
14 
15 protected:
16     Account(const Date& date, const string& id);
17 
18     void record(const Date& date, double amount, const string& desc);
19     void error(const string& msg) const;
20 
21 public:
22     const string& getId() { return id; }
23     double getBalance() const { return balance; }
24     static double getTotal() { return total; }
25 
26     virtual void deposit(const Date& date, double amount, const string& desc) = 0;
27     virtual void withdraw(const Date& date, double amount, const string& desc) = 0;
28     virtual void settle(const Date& date) = 0;
29 
30     virtual void show() const;
31 };
32 
33 
34 class SavingsAccount : public Account {
35 private:
36     Accumulator acc;
37     double rate;
38 
39 public:
40     SavingsAccount(const Date& date, const string& id, double rate);
41 
42     double getRate() const { return rate; }
43 
44     void deposit(const Date& date, double amount, const string& desc);
45     void withdraw(const Date& date, double amount, const string& desc);
46     void settle(const Date& date);
47 };
48 
49 
50 class CreditAccount : public Account {
51 private:
52     Accumulator acc;
53     double credit;
54     double rate;
55     double fee;
56 
57     double getDebt() const {
58         double balance = getBalance();
59         return (balance < 0 ? balance : 0);
60     }
61 
62 public:
63     CreditAccount(const Date& date, const string& id, double credit, double rate, double fee);
64 
65     double getCredit() const { return credit; }
66     double getRate() const { return rate; }
67     double getFee() const { return fee; }
68     double getAvailableCredit() const {
69         if (getBalance() < 0) return credit + getBalance();
70         else return credit;
71     }
72 
73     void deposit(const Date& date, double amount, const string& desc);
74     void withdraw(const Date& date, double amount, const string& desc);
75     void settle(const Date& date);
76     void show() const;
77 };

account.cpp,

 1 #include "account.h"
 2 #include <cmath>
 3 #include<iostream>
 4 
 5 using namespace std;
 6 
 7 double Account::total = 0;
 8 
 9 Account::Account(const Date& date, const string& id) : id(id), balance(0) {
10     date.show();
11     cout << "\t#" << id << " created" << endl;
12 }
13 
14 void Account::record(const Date& date, double amount, const string& desc) {
15     amount = floor(amount * 100 + 0.5) / 100;
16     balance += amount;
17     total += amount;
18     date.show();
19     cout << "\t#" << id << "\t" << amount << "\t" << balance << "\t" << desc << endl;
20 }
21 
22 void Account::show() const {
23     cout << id << "\tBalance: " << balance;
24 }
25 
26 void Account::error(const string& msg) const {
27     cout << "Error (#" << id << "): " << msg << endl;
28 }
29 
30 
31 SavingsAccount::SavingsAccount(const Date& date, const string& id, double rate)
32     : Account(date, id), rate(rate), acc(date, 0) {}
33 
34 void SavingsAccount::deposit(const Date& date, double amount, const string& desc) {
35     record(date, amount, desc);
36     acc.change(date, getBalance());
37 }
38 
39 void SavingsAccount::withdraw(const Date& date, double amount, const string& desc) {
40     if (amount > getBalance()) {
41         error("not enough money");
42     }
43     else {
44         record(date, -amount, desc);
45         acc.change(date, getBalance());
46     }
47 }
48 
49 void SavingsAccount::settle(const Date& date) {
50     double interest = acc.getSum(date) * rate / (date - Date(date.getYear() - 1, 1, 1));
51     if (interest != 0) record(date, interest, "interest");
52     acc.reset(date, getBalance());
53 }
54 
55 
56 CreditAccount::CreditAccount(const Date& date, const string& id, double credit, double rate, double fee)
57     : Account(date, id), credit(credit), rate(rate), fee(fee), acc(date, 0) {}
58 
59 void CreditAccount::deposit(const Date& date, double amount, const string& desc) {
60     record(date, amount, desc);
61     acc.change(date, getDebt());
62 }
63 
64 void CreditAccount::withdraw(const Date& date, double amount, const string& desc) {
65     if (amount - getBalance() > credit) {
66         error("not enough credit");
67     }
68 
69     else {
70         record(date, -amount, desc);
71         acc.change(date, getDebt());
72     }
73 }
74 
75 void CreditAccount::settle(const Date& date) {
76     double interest = acc.getSum(date) * rate;
77     if (interest != 0) record(date, interest, "interest");
78     if (date.getMonth() == 1) record(date, -fee, "annual fee");
79     acc.reset(date, getDebt());
80 }
81 
82 void CreditAccount::show() const {
83     Account::show();
84     cout << "\tAvailable credit: " << getAvailableCredit();
85 }

8_8.cpp源码

 1 #include "account.h"
 2 #include<iostream>
 3 using namespace std;
 4 
 5 int main() {
 6     Date date(2008, 11, 1);
 7 
 8     SavingsAccount sa1(date, "S3755217", 0.015);
 9     SavingsAccount sa2(date, "02342342", 0.015);
10     CreditAccount ca(date, "C5392394", 10000, 0.0005, 50);
11 
12     Account* accounts[] = { &sa1, &sa2, &ca };
13     const int n = sizeof(accounts) / sizeof(Account*);
14 
15     cout << "(d)deposit (w)withdraw (s)show (c)change day (n)next month (e)exit" << endl;
16     char cmd;
17     do {
18         date.show();
19         cout << "\tTotal:" << Account::getTotal() << "\tcommand>";
20 
21         int index, day;
22         double amount;
23         string desc;
24         cin >> cmd;
25 
26         switch (cmd) {
27         case 'd':
28             cin >> index >> amount;
29             getline(cin, desc);
30             accounts[index]->deposit(date, amount, desc);
31             break;
32 
33         case 'w':
34             cin >> index >> amount;
35             getline(cin, desc);
36             accounts[index]->withdraw(date, amount, desc);
37             break;
38 
39         case 's':
40             for (int i = 0; i < n; i++) {
41                 cout << "[" << i << "]";
42                 accounts[i]->show();
43                 cout << endl;
44             }
45             break;
46 
47         case 'c':
48             cin >> day;
49             if (day < date.getDay()) {
50                 cout << "You cannot specify a previous day";
51             }
52             else if (day > date.getMaxDay())
53                 cout << "Invalid day";
54             else date = Date(date.getYear(), date.getMonth(), day);
55             break;
56 
57         case 'n':
58             if (date.getMonth() == 12)
59                 date = Date(date.getYear() + 1, 1, 1);
60             else date = Date(date.getYear(), date.getMonth() + 1, 1);
61             for (int i = 0; i < n; i++) {
62                 accounts[i]->settle(date);
63             }
64             break;
65         }
66 
67     } while (cmd != 'e');
68 
69     return 0;
70 }

运行截图：

用文字总结：本章第7章例7-10，这一版本做了哪些改进？这一版本迭代后，还有哪些问题有待解决/完善

加入了抽象类，利用了类的多态实现了代码复用。建立一个数组，各种对象都可以用数组的一个基类指针来访问，提高运行效率，使代码更为简洁。

posted @ 2024-12-08 23:55 安东尼23 阅读(30) 评论(0) 收藏举报

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实验5 继承和多态

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