问题描述

关于C++文件的读写read和write问题！

第一个：这样写读出结果会对，但是有时候也会出错。换成中文的有时也会出错。
#include
#include
#include

using namespace std;

class People
{
private:
struct
{
string name;
string weight;
string tall;
string sex;
}people;
public:
People(){}
People(string name, string weight, string tall, string sex)
{
people.name=name;
people.weight=weight;
people.tall=tall;
people.sex=sex;
}
string get_Name()
{
return people.name;
}
string get_Sex()
{
return people.sex;
}
};

int main()
{
fstream file;
file.open("people.txt",ios::out|ios::binary);
People pe("aaa","bbb","ccc","sda");
People pe2;
file.write(reinterpret_cast(&pe),sizeof(pe));
file.close();
file.open("people.txt",ios::in|ios::binary);
file.read(reinterpret_cast(&pe2),sizeof(pe2));
cout<<pe2.get_Sex()<<" "<<pe2.get_Name();
file.close();
return 0;
}

第二种：是第一种写的文件读出来，为什么就会出错？
#include
#include
#include

using namespace std;

class People
{
private:
struct
{
string name;
string weight;
string tall;
string sex;
}people;
public:
People(){}
People(string name, string weight, string tall, string sex)
{
people.name=name;
people.weight=weight;
people.tall=tall;
people.sex=sex;
}
string get_Name()
{
return people.name;
}
string get_Sex()
{
return people.sex;
}
};

int main()
{
fstream file;
People pe2;
file.open("people.txt",ios::in|ios::binary);
file.read(reinterpret_cast(&pe2),sizeof(pe2));
cout<<pe2.get_Sex()<<" "<<pe2.get_Name();
file.close();
return 0;
}

解决方案

string是动态类型，你sizeof方式求大小会有问题，造成数据读取不对。
结构体要用基本数据类型。

解决方案二：

能解释下为什么吗？还有我现在改成基本类型了。这个例子可以了。我还有另外一个例子，可以写，但是不可以读。能帮我看下吗？谢谢！
#include
#include
#include
#include

using namespace std;

const int NUM=1000;
static int employeerNum=0;
static int loadNum=0;

class Employeer
{
private:
struct
{
char name[30];
char gender[10];
char dateofbirth[30];
char category[30];
}employeerInfor;
public:
Employeer(char name[],char gender[],char dateofbirth[],char category[])
{
strcpy(employeerInfor.name,name);
strcpy(employeerInfor.gender,gender);
strcpy(employeerInfor.dateofbirth,dateofbirth);
strcpy(employeerInfor.category,category);
}//构造函数
char *Get_name()
{
return employeerInfor.name;
}
char *Get_gender()
{
return employeerInfor.gender;
}
char *Get_dateofbirth()
{
return employeerInfor.dateofbirth;
}
char *Get_category()
{
return employeerInfor.category;
}
virtual float computeSalary()=0;//纯虚函数
friend void Save(int i);
friend int ReadDate();
};

Employeer *employeer[NUM];

int ReadDate()
{
fstream outFile;
outFile.open("Manager.txt",ios::in|ios::binary);
if(outFile.fail())
{
return 0;
}
else
{
int i=loadNum;
while(!outFile.eof())
{
outFile.read((char *)&employeer[i]->employeerInfor,sizeof(employeer[i]->employeerInfor));
i++;
}
cout<<loadNum;
loadNum=i-1;
employeerNum=loadNum;//加载完成，总数变化
}
outFile.close();
}
int main()
{
ReadDate();
return 0;
}