Saving object having string in file - c++

Question

When I am running this program having error in reading file compiler show error of access violation please help me out in this matter I have tried << and >> operators for writing and reading but I am using next pointer due to which I cannot use these operator
#include<iostream>
#include<conio.h>
#include<string>
#include<fstream>
using namespace std;
class employee
{ private:
int id;
static int count;
public:
string name;
employee *next;
employee()
{ cout<<"enter name:";
cin>>name;
count++;
id=count;
next=NULL;
}
employee(int x)
{}
void setcount(int x)
{count=x;}
void show()
{cout<<"Name: "<<name<<endl;
cout<<"id: "<<id<<endl;
}
void setname(string s)
{name=s;}
string getname()
{return name;}
int getid()
{return id;}
};
int employee::count=0;
class db
{ employee *list;
public:
db ()
{ list=NULL; }
void hire()
{employee *e=new employee;
employee *temp=list;
if(list==NULL)
{list=e;}
else{
while(temp->next!=NULL)
{ temp=temp->next; }
temp->next=e;
}//else end
cout<<"hired..."<<endl;
}
void displayall()
{ if(list==NULL)
cout<<"NO record..";
else
{ employee *temp=list;
while(temp!=NULL)
{temp->show();
temp=temp->next; }
}//else end
}
void remove()
{ int id;
int found=0;
cout<<"Enter id to be removed...";
cin>>id;
if(list==NULL)
cout<<"no record..";
else
{ employee *temp=list;
employee *pre=list;
while(temp!=NULL)
{ if( temp->getid()==id)
{ found=1;
employee *e=temp;
e->show();
if(temp==list) //first item to b removed
list=list->next;
else
pre->next=temp->next;
delete e; cout<<"record deleted"<<endl;
break;
}
pre=temp;
temp=temp->next;
}//while end
if(found==0)
cout<<"record not found.."<<endl;
}//else end
}
void searchbyname()
{ string name;
int found=0;
cout<<"enter name..";
cin>>name;
if(list==NULL)
cout<<"no record..";
else
{ employee *temp=list;
while(temp!=NULL)
{ if( temp->getname()==name)
{ found=1;
temp->show();}
temp=temp->next;
}//while end
if(found==0)
cout<<"record not found.."<<endl;
}//else end
}
void save()
{ ofstream out;
out.open("eb",ios::out | ios::binary);
if(!out)
cout<<"cannot save..";
else
{ employee *temp=list;
while(temp!=NULL)
{ out.write((char*) temp,sizeof(employee));
temp=temp->next;
}
out.close();
}
}
void retrieve()
{ ifstream in;
in.open("eb",ios::in | ios::binary);
if(!in)
cout<<"cannot retrieve..";
else
{ employee *temp=NULL;
employee e(0);
while(1)
{ in.read((char*) &e,sizeof(employee));
employee *p=new employee(e); //dynamically creating an employee that will have the same value as 'e' and saving its address in p. Every node in link list has different location so p will be different. &e is always same. So actually read node from file in e than create a node dynamically with same contents and address will be save in p.
if(list==NULL)
{list=p;
temp=list;
p->show();}
else{
temp->next=p;
temp=temp->next;
e.show();
if(e.next==NULL)
{ e.setcount(e.getid()); break;}
}
}
in.close();
}
}
};
void main()
{
db obj;
try{ obj.retrieve();
int op;
while(1)
{ cout<<endl<<"Enter 1 to hire ,2 for remove ,3 for displayall, 4 for search by name.. 5 for exit";
cin>>op;
switch(op)
{case 1:
obj.hire(); break;
case 2:
obj.remove(); break;
case 3:
obj.displayall(); break;
case 4:
obj.searchbyname(); break;
}
if(op==5)
break;
}
obj.save();
}
catch(...)
{cout<<"error..";}
getch();
}

Answer 1

You can not read your class data from the file using this code: in.read((char*) &e,sizeof(employee)); Your class contains std::string and pointers, they will be initialized by the values, that point nowhere. Any attempt to use them is an undefined behavior, leading to the AV in your case.