如下定义了两个类，一个基类，一个派生类，然后定义了一个拍成类对象的链表，但是当使用getline（cin,astring）函数输入string成员时无法读取（getline第三个参数为默认），但当把getline（）函数第三个参数设置为某一个字符（如：getline（cin,astring,'#')时，可以读入，为什么？
class box{
protected:
     double height;
     double length;
     double wideth;
public:
     box(double heightvalue,double lengthvalue,double widethvalue);
     box();
     box(const box& abox);
     box& operator=(const box& abox);
     virtual   double volume();
     bool operator<(box& abox);
     friend double getwideth(box& abox);
     static double getlength(box& abox);
     double showvolume();
     double getheight()const{return height;};
     double getlength()const{return length;};
     double getwideth()const{return wideth;};
};
class carton:public box{
     public:
     string* pmentral;
     carton* next;
     double getheight();
     carton(string pstr="paple");
     carton(double heightvalue,double lengthvalue,double widethvalue,string pstr="paple",carton* next=NULL);
     carton(const carton& acarton);
     void getmentral(const carton& acarton);
     double volume();
     double showvolume();
     carton* createlist();
};
carton* carton::createlist()
{
     carton* head=NULL;
     carton* end=head;
     carton* ps;
     char ch;
     cout<<"Please input the value of the carton!"<<endl;
     string astring;
     do{
        
         double heightvalue=0;
         double lengthvalue=0;
         double widethvalue=0;
        
         cin>>heightvalue;
         cin>>lengthvalue;
         cin>>widethvalue;
        
         getline(cin,astring);                                 //此处为何读取不了输入的字符串？？？
         cout<<astring;
         ps=new carton(heightvalue,lengthvalue,widethvalue,astring);
         if(head==NULL)
         {
             head=ps;
         }
         else
         {
             end->next=ps;
         }
         end=ps;
        
         cout<<"Do you want to input again?"<<endl;
         cin.ignore(1024,'\n');
         cin>>ch;
         cout<<endl;
     }while(ch=='y'||ch=='Y');
     end->next=NULL;
//     ps->next=NULL;
//     delete ps;
     return head;
};

怎么没人啊，下面是全部代码：
#include <iostream>
#include <string>
using namespace std;
class box{
protected:
     double height;
    
     double length;
    
     double wideth;
public:
     box(double heightvalue,double lengthvalue,double widethvalue);
     box();
     box(const box& abox);
     box& operator=(const box& abox);
     virtual   double volume();
     bool operator<(box& abox);
     friend double getwideth(box& abox);
     static double getlength(box& abox);
     double showvolume();
     double getheight()const{return height;};
     double getlength()const{return length;};
     double getwideth()const{return wideth;};
};
box::box(double heightvalue,double lengthvalue,double widethvalue):
height(heightvalue),length(lengthvalue),wideth(widethvalue){};
box::box()
{
     height=length=wideth=1.0;
};
box::box(const box& abox)
{
     height=abox.height;
     length=abox.length;
     wideth=abox.wideth;
//     return *this;
};
box& box::operator=(const box& abox)
{
     height=abox.height;
     length=abox.length;
     wideth=abox.wideth;
     return *this;
};
double box::volume()
{
     cout<<"The box volume() do!"<<endl;
     return height*length*wideth;
};
bool box::operator<(box& abox)
{
     return volume()<abox.volume();
};
double box::showvolume()
{
     return volume();
};
class carton:public box{
//private:
     public:
     string* pmentral;
     carton* next;
//     double volume();
     double getheight();
     carton(string pstr="paple");
     carton(double heightvalue,double lengthvalue,double widethvalue,string pstr="paple",carton* next=NULL);
     carton(const carton& acarton);
     void getmentral(const carton& acarton);
     double volume();
     double showvolume();
     carton* createlist();
//     void showlist(carton* acarton)const;
};
carton::carton(string pstr)
{
     pmentral=new string(pstr);


};
carton::carton(double heightvalue,double lengthvalue,double widethvalue,string pstr,carton* next):
box(heightvalue,lengthvalue,widethvalue){
     pmentral=new string(pstr);
};
void carton::getmentral(const carton& acarton)
{
     cout<<*(acarton.pmentral)<<endl;
};
/*
double carton::volume()
{
     cout<<"The carton volume() do!"<<endl;
     return height*length*wideth;
}
*/
double carton::getheight()
{
     return height;
};
double getwideth(box& abox)
{
     return abox.wideth;
};
double box::getlength(box& abox)
{
     return abox.length;
};
double carton::volume()
{
     return 10*height*length*wideth;
};
double carton::showvolume()
{
     return volume();
};
class pallent:public carton{
private:
     double number;
public:
     pallent(double numbervalue);
     double getheight(){return height;};
     double getlength(){return length;};
     double getwideth(){return wideth;};
    
};
pallent::pallent(double numbervalue)
{
     number=numbervalue;
};
carton::carton(const carton& acarton):box(acarton){
     pmentral=new string(*acarton.pmentral);
//     strcpy(pmentral,acarton.pmentral);
     cout<<"The copy construction!"<<endl;
};
void showvolume(box& abox)
{
     cout<<"The main volume is :"<<abox.showvolume()<<endl;
};
carton* carton::createlist()
{
     carton* head=NULL;
     carton* end=head;
     carton* ps;
     char ch;
     cout<<"Please input the value of the carton!"<<endl;
     string astring;
     do{
        
         double heightvalue=0;
         double lengthvalue=0;
         double widethvalue=0;
        
         cin>>heightvalue;
         cin>>lengthvalue;
         cin>>widethvalue;
        
         getline(cin,astring);
         cout<<astring;
         ps=new carton(heightvalue,lengthvalue,widethvalue,astring);


//         acarton.pmentral=&astring;
         if(head==NULL)
         {
             head=ps;
         }
         else
         {
             end->next=ps;
         }
         end=ps;
        
         cout<<"Do you want to input again?"<<endl;
         cin.ignore(1024,'\n');
         cin>>ch;
         cout<<endl;
     }while(ch=='y'||ch=='Y');
     end->next=NULL;
//     ps->next=NULL;
//     delete ps;
     return head;
};
void showlist(carton* acarton)
{
     if(acarton!=NULL)
     {
         while(acarton!=NULL)
         {
              cout<<"The carton is :"<<acarton->getheight()<<" by "<<acarton->getlength()<<" by "<<acarton->getwideth()<<" by "<<*(acarton->pmentral)<<endl;
              acarton=acarton->next;
         }
     }
     cout<<"The list has over!"<<endl;
};
int main()
{
     box abox(20,30,40);
     carton acarton(30,40,50,"suliao");
     showvolume(abox);
     showvolume(acarton);
     box* pabox=&abox;
//     carton* pacarton=&acarton;
     cout<<"The volume of the abox is :"<<abox.volume()<<endl;
     cout<<"The volume of the acarton is :"<<acarton.volume()<<endl;
     cout<<"The volume of the pabox is :"<<pabox->volume()<<endl;
     pabox=&acarton;
     cout<<"The volume of the pacarton is :"<<pabox->volume()<<endl;
     /*
     cout<<"The volume of the abox is :"<<abox.volume()<<endl;
     cout<<"The volume of the acarton is :"<<acarton.volume()<<endl;
     cout<<"The wideth of the abox is :"<<getwideth(abox)<<endl;
     cout<<"The length of the abox is :"<<abox.getlength(abox)<<endl;
     */
     pallent apallent(50);
//     cout<<"The height of the pallent is :"<<apallent.height<<endl;
     carton tcarton=acarton;
     cout<<"The mentral of the acarton is :"<<endl;
     acarton.getmentral(tcarton);
     carton* ahead=acarton.createlist();
     showlist(ahead);
     return 0;
}


你输入的是什么？getline默认是'\n'……

回复：5楼
输入一个字符串，getline()第三个参数是终止字符啊，将它定义为换行‘\n’

回复：6楼
getline第三个默认参数是'\n'
你是不是输的
（1）（空格）（2）（空格）（3）（空格）（换行）
那么,astring得到的是空格，

正确的
输入可能如下：
输入（1）（空格）（2）（空格）（3）（C）（P）（P）（换行）
astring得到的是CPP

getline输入过数据没?