问：为什么这段代码不能正常运行？
我用C ++语言实现了文件处理。
我已经创建了一个完整的汽车文件。通过此代码，我们可以存储新数据，删除旧数据，搜索有关汽车的特定数据。问题是此代码成功编译但在运行时，其执行停止并显示错误消息。我请求帮助我从此代码中删除运行时错误。
CODE：
#include<iostream>
#include<string.h>
#include<conio.h>
#include<fstream>
using namespace std;
struct car
{
char name[20];
int model;
string color;
int car_id;
string size;
float weight;
int price;
};
void getdata(car&); //function declaration
void showdata(car&); //function declaration
void searchdata(); //function declaration
void deleterecord(); //function declaration
void modify(); //function declaration
void readdata(); //function declaration
void writedata(); //function declaration
int main()
{
char ch;
cout<<"\nEnter w to write record ";
cout<<"\nEnter r to read record";
cout<<"\nEnter m to modify record";
cout<<"\nEnter s to search record";
cout<<"\nEnter d to delete record";
cout<<"\n\nEnter your choice :";
cin>>ch;
switch(ch)
{
case 'w':
{
writedata();
break;
}
case 'r':
{
readdata();
break;
}
case 's':
{
searchdata();
break;
}
case 'd':
{
deleterecord();
break;
}
case 'm':
{
modify();
break;
}
default:
{
cout<<"\nWrong choice";
}
}
return 0;
}
void getdata(car &ccc)
{
cout<<"Please enter name of car :";
cin>>ccc.name;
cout<<"Please enter model number of car:";
cin>>ccc.model;
cout<<"Enter color of car:";
cin>>ccc.color;
cout<<"Enter id number of car:";
cin>>ccc.car_id;
cout<<"Enter size of car :";
cin>>ccc.size;
cout<<"Enter weight of a car :";
cin>>ccc.weight;
cout<<"Enter price of a car :";
cin>>ccc.price;
}
void showdata(car &ccc)
{
cout<<"\nName of car is :";
puts(ccc.name);
cout<<"\nModel number of car is :"<<ccc.model;
cout<<"\nColor of car is :"<<ccc.color;
cout<<"\nID number of car is :"<<ccc.car_id;
cout<<"\nSize of car is :"<<ccc.size;
cout<<"\nWeight of car is :"<<ccc.weight;
cout<<"\nPrice of car is :"<<ccc.price;
}
void writedata()
{
ofstream file;
char ch='y';
car ccc;
file.open("carinformation.dat",ios::binary | ios::out | ios::app);
while(ch=='y'|| ch=='Y')
{
getdata(ccc);
file.write((char*)&ccc,sizeof(ccc));
cout<<"\nDo you want to countine?";
cin>>ch;
}
file.close();
}
void readdata()
{
int count=0;
ifstream file;
car ccc;
file.open("carinformation.dat",ios::binary | ios::in);
if(!file)
{
cout<<"File not found";
exit(0);
}
else
{
file.read((char*)&ccc,sizeof(ccc));
while(!file.eof())
{
showdata(ccc);
file.read((char*)&ccc,sizeof(ccc));
count++;
}
cout<<"Number of records are :"<<count;
}
file.close();
}
void searchdata()
{
car ccc;
ifstream file;
char n_c[20];
cout<<"Enter name of car :";
cin>>n_c;
file.open("carinformation.dat",ios::binary | ios::in);
if(!file)
{
cout<<"File nnot found";
exit(0);
}
else
{
file.read((char*)&ccc, sizeof(ccc));
while(!file.eof())
{
if(strcmp(n_c,ccc.name)==0)
{
showdata(ccc);
}
file.read((char*)&ccc, sizeof(ccc));
}
}
file.close();
}
void modify()
{
car ccc;
fstream file;
char n_c[20];
file.open("carinformation.dat",ios::binary | ios::in | ios::out);
cout<<"\nEnter name of car that should be searched:";
cin>>n_c;
if(!file)
{
cout<<"File not found";
exit(0);
}
else
{
file.read((char*)&ccc,sizeof(ccc));
while(!file.eof())
{
if(strcmp(n_c,ccc.name)==0)
{
file.seekg(0, ios::cur);
cout<<"Enter new record :\n";
getdata(ccc);
int i=file.tellg();
int j=sizeof(ccc);
int k=i-j;
file.seekp(k);
file.write((char*)&ccc, sizeof(ccc));
}
}
}
file.read((char*)&ccc, sizeof(ccc));
file.close();
}
void deleterecord()
{
int count=0;
car ccc;
int c_id;
cout<<"Please enter car id :";
cin>>c_id;
ifstream file;
file.open("carinformation.dat" ,ios::binary| ios::in);
ofstream file2;
file2.open("New carinformation.dat", ios::binary| ios::out);
while(file.read((char*)&ccc,sizeof(ccc)))
{
if(ccc.car_id!=c_id)
{
file2.write((char*)&ccc ,sizeof(ccc));
count++;
}
}
cout<<"Number of records are :"<<count;
file2.close();
count=0;
file2.open("New carinformation.dat", ios::binary| ios::in);
file.read((char*)&ccc,sizeof(ccc));
while(!file.eof())
{
count++;
showdata(ccc);
file.read((char*)&ccc,sizeof(ccc));
}
cout<<"Number of records are :"<<count;
file.close();
file2.close();
remove("carinfomation.dat");
rename("New carinformation.dat", "carinformation.dat");
file.open("carinformation.dat", ios::binary | ios::in);
file.read((char*)&ccc, sizeof(ccc));
while(!file.eof())
{
count++;
showdata(ccc);
file.read((char*)&ccc, sizeof(ccc));
}
cout<<"Number of records are :"<<count;
}
答案 0 :(得分：2)
类car具有std::string个字段，这些字段保存指向堆分配内存的指针。因此，通过写入原始字节file.write((char*)&ccc,sizeof(ccc));将其保存到文件中是行不通的。而且，更重要的是，稍后阅读file.read((char*)&ccc, sizeof(ccc));将使用无效指针值填充字符串对象。您需要逐个存储字段并逐个仔细地读取输入数据。
答案 1 :(得分：0)
“string”和“string.h”之间存在差异。删除两个字符“.h”并查看您的代码是否有效。
<string.h> contains functions like strcpy, strlen for C style null-terminated strings.
<string> contains std::string, std::wstring plus other classes.
你需要初始化你的结构，这是你的readdata（）的一个例子，查看更改并找出如何修复程序的其余部分：
void readdata()
{
int count=0;
ifstream file;
car *ccc = new car();
file.open("carinformation.dat",ios::binary | ios::in);
if(!file)
{
cout<<"File not found";
exit(0);
}
else
{
file.read((char*)ccc,sizeof(*ccc));
while(!file.eof())
{
showdata(*ccc);
file.read((char*)ccc,sizeof(*ccc));
count++;
}
cout<<"Number of records are :"<<count;
}
file.close();
}