13.1.2 纯虚函数(Pure Virutal Functions)

#ifndef HEADER_ACCOUNT
#define HEADER_ACCOUNT

#include<string>
using std::string;
class Account
{
     string acntNumber;
	 double balance;
public:
	 //构造函数
	 Account(string _acntNumber, double _balance=0.0);
	 //定义一个虚函数display并定义为const型
	 virtual void display()const;
	 //定义返回double类型函数getBalance
	 double getBalance(){ return balance;}
	 //定义void型函数，参数为double型,对balance变量进行加操作
	 void deposit(double amount){ balance += amount;}
	 
	 //定义重载运算符==
	 //右边的参数为一个Account类型的引用a
	 //而右边的参数当前类型自己
	 //如果为等于返回true否则返回falsh
	 bool operator==(const Account& a)const{
		std::cout<<"acntNumber:"<<acntNumber<<" = a.acntNumber"<<a.acntNumber<<"\n";
	    return balance == a.balance;
	 }

	 //定义一个虚函数withdrawal，一会儿进行声明纯虚函数
	 virtual void withdrawal(double amount);
};
#endif

　　

#include <iostream>
#include "account.h"

Account::Account(string _acntNumber, double _balance):acntNumber(_acntNumber),balance(_balance){};

void Account::display()const{
   std::cout<<"acntNumber:"<<acntNumber<<", balance:"<<balance<<"\n";
};

void Account::withdrawal(double amount){
   balance += amount;
};

　　

 

//我们引入抽像类(Abstract Classes)的概念，抽像类的用途是被继承
//定义抽像类就是在类定义中至少声明一个纯虚函数Virtual,
/**/
#include <iostream>
#include "account.h";
int main()
{
//定义小向
//Account *a = new Account("小向",22.11);
//a->display();

//定义小菊
//Account *b = new Account("小菊",22.11);
//b->display();

//给小向加上一百元
//a->deposit(100);
//给小菊加上十元
//b->deposit(100);

//现在对比两个人的帐户金额是否相同
//bool isok=false;
//这里并没有调用重载运算符operator==
//isok = a==b;
//a->operator==b;
//isok = a.operator==b;
//这里停一下，重载运算符调用不成功样，得先去学习一下重载运算符

Account a("小向",22.11);
Account b("小菊",22.11);

if(a == b){
std::cout<<"相等\n";
}else
std::cout<<"不相等\n";
system("pause");
return 0;
}