《C++PrimerPlus》第13章类继承

13.1 一个简单的基类

基类和派生类示例（球会会员管理）

头文件tabtenn1.h

#ifndef __TABTENN1_H__
#define __TABTENN1_H__#include <iostream>
#include <string>using namespace std;class TableTennisPlayer
{private:string firstname; string lastname;bool hasTable; // 是否有球桌public:TableTennisPlayer(const string &fn = "none", const string &ln = "none", bool ht = false);void Name() const;bool HasTable() const{return hasTable;}void ResetTable(bool v){hasTable = v;}
};class RatedPlayer : public TableTennisPlayer // 派生类
{
private:unsigned int rating; // 比分
public:RatedPlayer(unsigned int r = 0, const string &fn = "none", const string &ln = "none", bool ht = false); // 构造函数RatedPlayer(unsigned int r, const TableTennisPlayer &tp); // 构造函数unsigned int Rating() const { return rating; } // 显示比分void ResetRating(unsigned int r) { rating = r; } // 复位比分
};#endif

源代码main.cpp

#include <iostream>
#include "tabtenn1.h"using namespace std;int main(void)
{RatedPlayer rplay1(1140, "Mallory", "Duck", false);rplay1.Name(); // 派生类使用基类的成员函数if (rplay1.HasTable())cout << ": has a table." << endl;elsecout << ": hasn't a table." << endl;rplay1.Name();cout << ": Rating: " << rplay1.Rating() << endl;TableTennisPlayer player1("Tara", "Boomdea", false);RatedPlayer rplayer2(1212, player1); // 调用第二个构造函数cout << "Name: ";rplayer2.Name();cout << ": Rating : " << rplayer2.Rating() << endl;return 0;
}

源代码tabtenn1.cpp

#include "tabtenn1.h"TableTennisPlayer::TableTennisPlayer(const string &fn, const string &ln, bool ht)
{firstname = fn;lastname = ln;hasTable = ht;
}void TableTennisPlayer::Name() const
{cout << lastname << ", " << firstname;
}RatedPlayer::RatedPlayer(unsigned int r, const string &fn, const string &ln, bool ht) : TableTennisPlayer(fn, ln, ht) {rating = r;
}RatedPlayer::RatedPlayer(unsigned int r, const TableTennisPlayer &tp) : TableTennisPlayer(tp) { // 调用基类的复制构造函数（隐式调用，编译器自动生成）rating = r;
}

13.2 继承：is-a关系

13.3 多态公有继承

多态公有继承示例（银行的两类账户）

头文件brass.h

#ifndef __BRASS_H__
#define __BRASS_H__#include <iostream>
#include <string>
using namespace std;class Brass {
private:string fullName; // 客户姓名long acctNum; // 账号double balance; // 当前结余
public:Brass(const string &s = "Null", long an = -1,double bal = 0.0); // 创建账户（构造函数）void Deposit(double amt); // 存款virtual void Withdraw(double amt); // 取款（虚）double Balance() const; // 显示当前余额virtual void ViewAcct() const; // 显示账户信息（虚）virtual ~Brass(){}
};class BrassPlus : public Brass { // 派生类
private:double maxLoan; // 透支上限double rate; // 透支利率double owesBank; // 当前的透支总额
public:BrassPlus(const string &s = "Null", long an = -1, double bal = 0.0,double ml = 500.0, double rate = 0.11125); // 构造函数BrassPlus(const Brass &ba, double ml = 500.0, double rate = 0.11125); // 构造函数virtual void ViewAcct() const; // 显示账户信息（多态）（虚）virtual void Withdraw(double amt); // 取款（虚）void ResetMax(double m) { maxLoan = m; } // 修改存款最大值void ResetRate(double r) { rate = r; } // 修改利率void ResetOwes() { owesBank = 0.0; } // 将透支总额复位为0
};#endif // !__BRASS_H__

源代码main.cpp

#include "brass.h"const int CLIENTS = 3;int main()
{Brass Rick("Rick", 123456, 4000.0);BrassPlus Jack("Jack", 654321, 3000.0);Rick.ViewAcct();cout << endl;Jack.ViewAcct();cout << endl;cout << "Depositing $1000 into the Jack Account." << endl;Jack.Deposit(1000);Jack.ViewAcct();cout << endl;cout << "Withdraw $4200 from the Rick Account." << endl;Rick.Withdraw(4200);Rick.ViewAcct();cout << endl;cout << "Withdraw $4200 from the Jack Account." << endl;Jack.Withdraw(4200);Jack.ViewAcct();cout << endl;/*******************使用引用或指针************************/// 使用基类指针：可以指向基类对象，也可以指向派生类对象Brass *p_clients[CLIENTS]; //基类的指针数组，每个元素都是一个基类的指针string temp;long tempnum;double tempbal;int kind;for (int i = 0; i < CLIENTS; i++) {cout << "Enter the client's name: ";getline(cin, temp);cout << "Enter client's account number: ";cin >> tempnum;cout << "Enter opening balance: $";cin >> tempbal;cout << "Enter 1 for Brass Account or 2 for BrassPlus Account: ";while (cin >> kind && (kind != 1 && kind != 2))cout << "Please enter either 1 or 2: ";if (kind == 1)p_clients[i] = new Brass(temp, tempnum, tempbal); // 对类使用new，将会调用相应的构造函数else {double tmax, trate;cout << "Enter the overdraft limit: $";cin >> tmax;cout << "Enter the rate: ";cin >> trate;p_clients[i] = new BrassPlus(temp, tempnum, tempbal, tmax, trate);}while (cin.get() != '\n'); // 消耗掉回车}cout << endl;for (int i = 0; i < CLIENTS; i++) {// 虚方法，根据指针引用的对象来确定用哪种方法p_clients[i]->ViewAcct(); // 注意通过指针调用，用的是->cout << endl;}for (int i = 0; i < CLIENTS; i++) {// 必须要有虚析构函数，根据指针引用的对象来确定用哪种析构函数delete p_clients[i]; // 有new就有delete！}return 0;
}

源代码brass.cpp

#include "brass.h"Brass::Brass(const string &s, long an, double bal) {fullName = s;acctNum = an;balance = bal;
}void Brass::Deposit(double amt) {if (amt < 0)cout << "Negative value is not allowed!" << endl;elsebalance += amt;
}void Brass::Withdraw(double amt) {if (amt < 0)cout << "Negative value is not allowed!" << endl;else if (amt <= balance)balance -= amt;elsecout << "Withdraw amount exceeded your balance!" << endl;
}double Brass::Balance() const {return balance;
}void Brass::ViewAcct() const {cout << "Client: " << fullName << endl;cout << "Account number: " << acctNum << endl;cout << "Balance: $" << balance << endl;
}BrassPlus::BrassPlus(const string &s, long an, double bal, double ml,double r) : Brass(s, an, bal) {maxLoan = ml;rate = r;owesBank = 0.0;
}BrassPlus::BrassPlus(const Brass &ba, double ml, double r) : Brass(ba) {maxLoan = ml;rate = r;owesBank = 0.0;
}void BrassPlus::ViewAcct() const { // 定义的时候不需要加virtualBrass::ViewAcct(); // 派生类调用基类方法cout << "Maxium load: $" << maxLoan << endl;cout << "Loan Rate: " << rate << endl;cout << "Owed to bank: $" << owesBank << endl;
}void BrassPlus::Withdraw(double amt) {double bal = Balance();if (amt <= bal) // 取的钱小于余额Brass::Withdraw(amt);else if (amt <= bal + maxLoan - owesBank) { // 透支取钱double advance = amt - bal; // 透支的钱owesBank = advance * (1.0 + rate); // 欠银行的钱（加上利息）cout << "Bank Advance: $" << advance << endl;cout << "Finance charge: $" << advance * rate << endl;Deposit(advance); // 存钱Brass::Withdraw(amt); // 取钱}else // 透支也不够取cout << "Credit limit exceeded!" << endl;}

13.4 静态联编和动态联编

13.5 访问控制：protected

13.6 抽象基类

抽象类示例（银行的两类账户）

头文件acctabc.h

#ifndef __ACCTABC_H__
#define __ACCTABC_H__#include <iostream>
#include <string>
using namespace std;class AcctABC {
private:string fullName;long acctNum;double balance;
protected:const string &FullName() const { return fullName; } // 返回客户姓名long AcctNum() const { return acctNum; } // 返回客户账号
public:AcctABC(const string &s = "Null", long an = -1,double bal = 0.0); // 构造函数void Deposit(double amt); // 存款virtual void Withdraw(double amt) = 0; // 取款（纯虚函数）double Balance() const { return balance; } // 显示当前余额virtual void ViewAcct() const = 0; // 显示账户信息（纯虚函数）virtual ~AcctABC(){} // 析构函数（虚函数）
};class Brass : public AcctABC{
public:Brass(const string &s = "Null", long an = -1,double bal = 0.0) : AcctABC(s, an, bal) {} // 创建账户（构造函数）virtual void Withdraw(double amt); // 取款（虚）virtual void ViewAcct() const; // 显示账户信息（虚）virtual ~Brass(){}
};class BrassPlus : public AcctABC{ // 派生类
private:double maxLoan; // 透支上限double rate; // 透支利率double owesBank; // 当前的透支总额
public:BrassPlus(const string &s = "Null", long an = -1, double bal = 0.0,double ml = 500.0, double rate = 0.11125); // 构造函数BrassPlus(const Brass &ba, double ml = 500.0, double rate = 0.11125); // 构造函数virtual void ViewAcct() const; // 显示账户信息（多态）（虚）virtual void Withdraw(double amt); // 取款（虚）void ResetMax(double m) { maxLoan = m; } // 修改存款最大值void ResetRate(double r) { rate = r; } // 修改利率void ResetOwes() { owesBank = 0.0; } // 将透支总额复位为0
};#endif // !__BRASS_H__

源代码main.cpp

#include "acctabc.h"const int CLIENTS = 3;int main()
{AcctABC *p_clients[CLIENTS]; //基类的指针数组，每个元素都是一个基类的指针string temp;long tempnum;double tempbal;int kind;for (int i = 0; i < CLIENTS; i++) {cout << "Enter the client's name: ";getline(cin, temp);cout << "Enter client's account number: ";cin >> tempnum;cout << "Enter opening balance: $";cin >> tempbal;cout << "Enter 1 for Brass Account or 2 for BrassPlus Account: ";while (cin >> kind && (kind != 1 && kind != 2))cout << "Please enter either 1 or 2: ";if (kind == 1)p_clients[i] = new Brass(temp, tempnum, tempbal); // 对类使用new，将会调用相应的构造函数else {double tmax, trate;cout << "Enter the overdraft limit: $";cin >> tmax;cout << "Enter the rate: ";cin >> trate;p_clients[i] = new BrassPlus(temp, tempnum, tempbal, tmax, trate);}while (cin.get() != '\n'); // 消耗掉回车}cout << endl;for (int i = 0; i < CLIENTS; i++) {// 虚方法，根据指针引用的对象来确定用哪种方法p_clients[i]->ViewAcct(); // 注意通过指针调用，用的是->cout << endl;}for (int i = 0; i < CLIENTS; i++) {// 必须要有虚析构函数，根据指针引用的对象来确定用哪种析构函数delete p_clients[i]; // 有new就有delete！}return 0;
}

源代码acctabc.cpp

#include "acctABC.h"AcctABC::AcctABC(const string &s, long an, double bal) {fullName = s;acctNum = an;balance = bal;
}void AcctABC::Deposit(double amt) {if (amt < 0)cout << "Negative value is not allowed!" << endl;elsebalance += amt;
}void AcctABC::Withdraw(double amt) {balance -= amt;
}void Brass::Withdraw(double amt) {if (amt < 0)cout << "Negative value is not allowed!" << endl;else if (amt <= Balance())AcctABC::Withdraw(amt);elsecout << "Withdraw amount exceeded your balance!" << endl;
}void Brass::ViewAcct() const {cout << "Client: " << FullName() << endl;cout << "Account number: " << AcctNum() << endl;cout << "Balance: $" << Balance() << endl;
}BrassPlus::BrassPlus(const string &s, long an, double bal, double ml,double r) : AcctABC(s, an, bal) {maxLoan = ml;rate = r;owesBank = 0.0;
}BrassPlus::BrassPlus(const Brass &ba, double ml, double r) : AcctABC(ba) {maxLoan = ml;rate = r;owesBank = 0.0;
}void BrassPlus::ViewAcct() const { // 定义的时候不需要加virtualcout << "Client: " << FullName() << endl;cout << "Account number: " << AcctNum() << endl;cout << "Balance: $" << Balance() << endl;cout << "Maxium load: $" << maxLoan << endl;cout << "Loan Rate: " << rate << endl;cout << "Owed to bank: $" << owesBank << endl;
}void BrassPlus::Withdraw(double amt) {double bal = Balance();if (amt <= bal) // 取的钱小于余额AcctABC::Withdraw(amt);else if (amt <= bal + maxLoan - owesBank) { // 透支取钱double advance = amt - bal; // 透支的钱owesBank = advance * (1.0 + rate); // 欠银行的钱（加上利息）cout << "Bank Advance: $" << advance << endl;cout << "Finance charge: $" << advance * rate << endl;Deposit(advance); // 存钱AcctABC::Withdraw(amt); // 取钱}else // 透支也不够取cout << "Credit limit exceeded!" << endl;}

13.7 继承和动态内存分配

继承和动态内存分配示例（派生类使用或不使用new）

头文件dma.h

#ifndef __DMA_H___
#define __DMA_H___#include <iostream>
using namespace std;class baseDMA {
private:char *label;int rating;
public:baseDMA(const char *l = "null", int r = 0); // 构造函数baseDMA(const baseDMA &rs); // 复制构造函数virtual ~baseDMA(); // 析构函数（虚）baseDMA &operator=(const baseDMA &s); // 重载=运算符friend ostream &operator<<(ostream &os, const baseDMA &rs); // 重载<<运算符
};class lacksDMA : public baseDMA {
private:enum { COL_LEN = 40 };char color[COL_LEN];
public:lacksDMA(const char *l = "null", int r = 0, const char *c = "blank"); // 构造函数lacksDMA(const baseDMA &rs, const char *c = "blank");friend ostream &operator<<(ostream &os, const lacksDMA &rs);
};class hasDMA : public baseDMA {
private:char *style;
public:hasDMA(const char *l = "null", int r = 0, const char *s = "none");hasDMA(const baseDMA &rs, const char *s);hasDMA(const hasDMA &hs); // 复制构造函数~hasDMA(); // 析构函数hasDMA &operator=(const hasDMA &hs); // 重载=运算符friend ostream &operator<<(ostream &os, const hasDMA &rs); // 重载<<运算符
};#endif

源代码main.cpp

#include "dma.h"int main()
{baseDMA shirt("Protabelly", 8);cout << "Displaying baseDMA object: " << endl;cout << shirt;cout << "-----------------------------------" << endl;lacksDMA ballon("Blimpo", 4, "red");cout << "Displaying lacksDMA object: " << endl;cout << ballon;cout << "-----------------------------------" << endl;lacksDMA ballon2(ballon); // 调用默认复制构造函数cout << ballon2;cout << "-----------------------------------" << endl;hasDMA map("Keys", 5, "Mercator");cout << "Displaying hasDMA object: " << endl;cout << map << endl;cout << "-----------------------------------" << endl;hasDMA map2 = map; // 使用复制构造函数cout << map2 << endl;cout << "-----------------------------------" << endl;hasDMA map3; map3 = map; // 使用重载赋值运算符cout << map3 << endl;return 0;
}

源代码dma.cpp

#include "dma.h"
#include <cstring>baseDMA::baseDMA(const char *l, int r) {label = new char[strlen(l) + 1];strcpy_s(label, strlen(l) + 1, l);rating = r;
}baseDMA::baseDMA(const baseDMA &rs) {label = new char[strlen(rs.label) + 1];strcpy_s(label, strlen(rs.label) + 1, rs.label);rating = rs.rating;
}baseDMA::~baseDMA() {delete[] label;
}baseDMA &baseDMA::operator=(const baseDMA &rs) {if (this == &rs) return *this;delete[] label;label = new char[strlen(rs.label) + 1];strcpy_s(label, strlen(rs.label) + 1, rs.label);rating = rs.rating;return *this;
}ostream &operator<<(ostream &os, const baseDMA &rs) {os << "Label: " << rs.label << endl;os << "Rating: " << rs.rating << endl;return os;
}lacksDMA::lacksDMA(const char *l, int r, const char *c) : baseDMA(l, r) {strncpy_s(color, COL_LEN, c, strlen(c)); // 注意strncpy和strncpy_s的区别
}lacksDMA::lacksDMA(const baseDMA &rs, const char *c) : baseDMA(rs) {strncpy_s(color, COL_LEN, c, strlen(c));
}ostream &operator<<(ostream &os, const lacksDMA &ls) {os << (const baseDMA &)ls; // 强制类型转换，使用基类的运算符输出基类的信息os << "Color: " << ls.color << endl;return os;
}hasDMA::hasDMA(const char *l, int r, const char *s) : baseDMA(l, r) {style = new char[strlen(s) + 1];strcpy_s(style, strlen(s) + 1, s);
}hasDMA::hasDMA(const baseDMA &rs, const char *s) : baseDMA(rs) {style = new char[strlen(s) + 1];strcpy_s(style, strlen(s) + 1, s);
}hasDMA::hasDMA(const hasDMA &hs) : baseDMA(hs) {cout << "Copy construct function." << endl; // 标记一下复制构造函数被使用style = new char[strlen(hs.style) + 1];strcpy_s(style, strlen(hs.style) + 1, hs.style);
}hasDMA::~hasDMA() {delete[] style;
}hasDMA &hasDMA::operator=(const hasDMA &hs) {cout << "operator function." << endl; // 标记重载赋值运算符被使用if (this == &hs) return *this;// 基类的重载运算符的函数表示法，传递给this指针// 这里不能写出this，否则会无限递归baseDMA::operator=(hs);delete[] style;style = new char[strlen(hs.style) + 1];strcpy_s(style, strlen(hs.style) + 1, hs.style);return *this;
}ostream &operator<<(ostream &os, const hasDMA &hs) {os << (const baseDMA &)hs; // 强制类型转换，使用基类的运算符输出基类的信息os << "Style: " << hs.style << endl;return os;
}