cpp随笔2——继承实战——账户

题目如下：

根据16.12节报定义的Account类、Savings类和Checking类，编写一个应用程序，它读入一系列账号和存款，创建若干储蓄和结算账户，直到碰到一个标志结束符号。并输出所有账号的存款数据

Account类：
class Account
{
public:
  Account(unsigned accNo, float balan=0.0); //
  unsigned AccountNo();
  float AcntBalan();
  static Account*& First();
  Account* Next();
  static int NoAccounts();
  void Display();
  void Deposit(float amount);
  virtual void Withdrawal(float amount);
protected:
  static Account* pFirst;
  Account* pNext;
  static int count;
  unsigned acntNumber;
  float balance;
};
 
Saving类：
class Savings :public Account
{
public:
       Savings(unsigned accNo, float balan=0.0);
       virtual void Withdrawal(float amount);
protected:
        static float minbalance;
};
 
Checking类：
class Checking :public Account
{
public:
     Checking(unsigned accNo, float balan=0.0);
      virtual void Withdrawal(float amount);
      void SetRemit(REMIT re);
protected:
       REMIT remittance;
};
其中，enum REMIT{remitByPost,remitByCable,other}; //无，信汇，电汇

//account.h

#ifndef account
#define account//防止反复调用
class Account
{
    public:
        Account(unsigned accNo,float balan =0.0);
        unsigned AccountNo();
        float AcntBalan();
        static Account * First();
        Account * Next();
        static int NoAccounts();
        void Display();
        void Deposit(float amount);
        virtual void Withdrawal(float amount);
    protected:
        static Account *pFirst;
        Account *pNext;
        static int count;
        unsigned acntNumber;
        float balance;
};
#endif

1.我们可以看到，account类中有两个指针，一个是Account *First 一个是Account *Next，我们可以认为两个函数返回的就是这两个指针。我们可以认为这是要实现一个链表结构来存放一系列数据

2,在account.h中，Account *First前有一个static关键词，很明显，链表的开头只能有一个，因此，我们需要定义其为static，表明这个变量是和类本身联系在一起的，而跟变量没有联系。这是什么意思呢，意思是两个Account变量的First是一个值，比如对象A的static int s=1，那么同一类的对象B的static int s=1，且两者是同时变化的

//account.cpp

#include <iostream>
#include "account.h"
using namespace std;
Account * Account::pFirst=0;
int Account::count=0;
Account::Account(unsigned accNo,float balan)//在链表后添加元素 
{
    acntNumber=accNo;
    balance=balan;
    pNext=0;
    count++;
    if(pFirst==0)
    pFirst=this;//this 表示本变量的地址 
    else
    {
        Account * pS=pFirst;
        for(;pS->pNext;pS=pS->pNext);//pS指向已有链表的最后一节 
        pS->pNext=this;
    }
    pNext=0;
}
unsigned Account::AccountNo()
{
    return acntNumber;
}
float Account::AcntBalan()
{
    return balance;
}
Account * Account::First()
{
    return pFirst;
}
Account* Account::Next()
{
    return pNext;
}
int Account::NoAccounts()
{
    return count;
}
void Account::Display()
{
    cout<<"Account number:"<<acntNumber<<endl;
    cout<<"balance = "<<balance <<endl;
    }
void Account::Deposit(float amount)
{
    balance+=amount;
}
void Account::Withdrawal(float amount)
{
    return;
}

注意在链表最后添加元素的方法与分类讨论

注意this 的用法（在构造函数中将对象添加在链表最后）

//savings.h

#ifndef savings
#define savings
#include "account.h"

class Savings:public Account
{
    public:
        Savings(unsigned accNo,float balan=0.0);
        virtual void Withdrawal(float amount);
};
#endif

//savings.cpp

#include <iostream>
#include "account.h"
#include "savings.h"
using namespace std;
Savings::Savings(unsigned accNo,float balan)
        :Account(accNo,balan){}
void Savings::Withdrawal(float amount)
{
    if(balance<amount)
    cout<<"Insufficient funds:balance"<<balance
    <<",withdrawal"<<amount<<endl;
    else
    balance-=amount;
}
//savings.cpp

可以看到这里使用了一个virtual，这是用来实现函数的多态性。基类中也有一个virtual函数，用来提示编译器在编译的时候判断调用的是哪边的函数

 

 

//checking.h

#ifndef checking
#define checkint
#include "account.h"
enum REMIT{remitByPost,remitByCable,other};
class Checking:public Account
{
    public:
        Checking (unsigned accNo,float balan=0.0);
        virtual void Withdrawal(float amount);
        void SetRemit(REMIT re);
    protected:
        REMIT remittance;
};
#endif

//checking.cpp

#include <iostream>
#include "account.h"
#include "checking.h"
using namespace std;
Checking::Checking(unsigned accNo,float balan):Account(accNo,balan)
{
    remittance=other;
}
void Checking::Withdrawal(float amount)
{
    float temp=amount;
    if(remittance=remitByPost)
    temp=amount+30;
    else if(remittance=remitByCable)
    temp=amount+60;
    if(balance<temp)
    cout<<"Insufficient funds:balance "<<balance
    <<",withdrawal"<<temp<<endl;
    else
    balance-=temp;
}
void Checking::SetRemit(REMIT re)
{
    remittance=re;
}

注意checking中的withdraw，根据汇款方式的不同加收费用（虽然和题干没有什么关系就是了）

 

 

#include <iostream>
#include "savings.h"
#include "account.h"
#include "checking.h"
using namespace std;
int main()
{
    /*输入*/ 
    cout<<"Input the accountNo and saving"<<endl;
    Savings*pS;
    pS=NULL;
    unsigned aN;
    float val;
    cin>>aN>>val;
    while(aN)
    {
        pS=new Savings(aN,val);
        cout<<"Input the accountNo and saving"<<endl;
        cin>>aN>>val;
    }
    
    /*输出*/ 
    for(Savings*p=(Savings*)pS->First();p;p=(Savings*)p->Next())//注意First返回的是Account* 指针，因此需要进行强制转换 
    cout<<p->AccountNo()<<"  "<<p->AcntBalan()<<endl;
    /*释放内存*/
    for(Savings*p=(Savings*)pS->First();p;)
    {
        Savings*t=p;
        p=(Savings*)p->Next();
        delete t;
    }
    
    /*输入*/ 
    Checking *pC;
    pC=NULL;
    cout<<"Input the accountNo and checking"<<endl;
    cin>>aN>>val;
    while(aN)
    {
        pC=new Checking(aN,val);
        cout<<"Input the accountNo and checking"<<endl;
        cin>>aN>>val;
    }
    
    /*输出*/ 
    for(Checking*p=(Checking*)pC->First();p;p=(Checking*)p->Next())
    cout<<p->AccountNo()<<"  "<<p->AcntBalan()<<endl;
    /*释放内存*/
    for(Checking*p=(Checking*)pC->First();p;)
    {
        Checking*t=p;
        p=(Checking*)p->Next();
        delete t;
    }

}

最后就是主函数了，注意指针类型的强制转换和内存的new、delete