将对象的类类型保存到文件并在 C++ 中读回
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【中文标题】将对象的类类型保存到文件并在 C++ 中读回【英文标题】：Saving an Object's class type to file and reading it back in C++ 【发布时间】：2014-10-27 09:37:55 【问题描述】：我的程序是我有一个抽象员工类，它有 3 个继承子类，经理、研究员和工程师。
所有 3 个都有 3 个公共数据，然后是他们自己的数据要存储。
这 3 个类必须通过指向 Employee 类的指针向量存储，然后向下转换每个元素。
最后，它具有保存到文件和从文件加载的功能。
除了加载数据之外，我可以做其他所有事情。问题是在代码的开头，我如何定义向量的每个元素都是特定的继承类；例如：vec[0] 是经理，vex[1] 是工程师，等等。
这是我的所有代码。我试过的问题代码在 void MenuControl() Switch Case 5 中。
#ifndef EMPLOYEE_H
#define EMPLOYEE_H
#include<iostream>
#include <string>
#include <fstream>
using namespace std;
class Employee
public:
Employee();
virtual void BasicInfo()=0;
virtual void DisplayInfo()=0;
virtual void SaveInfo(ofstream& outFile)=0;
virtual void LoadInfo(ifstream& inFile)=0;
~Employee();
protected:
string f_Name, l_Name;
int salary;
;
Employee::Employee()
Employee::~Employee()
void Employee::BasicInfo()
void Employee::DisplayInfo()
#endif
#ifndef MANAGER_H
#define MANAGER_H
#include<iostream>
#include <string>
#include <fstream>
#include "Employee.h"
using namespace std;
class Manager : public Employee
public:
Manager();
Manager(string fName, string lName, int sal);
void BasicInfo();
void DisplayInfo();
void SaveInfo(ofstream& outFile);
void LoadInfo(ifstream& inFile);
~Manager();
protected:
int vacation, meets;
;
#endif
//Manager::Manager(string fName, string lName, int sal) : Employee(f_Name, l_Name, salary)
Manager::Manager()
Manager::Manager(string fName, string lName, int sal)
f_Name = fName;
l_Name = lName;
salary = sal;
void Manager::BasicInfo()
cout<<endl<<"Enter Number of Vacations: ";
cin>>vacation;
cout<<endl<<"Enter Number of Meetings: ";
cin>>meets;
void Manager::DisplayInfo()
cout<<endl<<endl<<"TYPE: Manager";
cout<<endl<<"Name: "<<f_Name<<" "<<l_Name;
cout<<endl<<"Salary: "<<salary<<endl;
cout<<"Number of Vacations: "<<vacation;
cout<<endl<<"Meetings per Week: "<<meets;
cout<<endl<<endl<<endl;
Manager::~Manager()
void Manager::SaveInfo(ofstream& outFile)
outFile.write((char*)&f_Name, sizeof(string));
outFile.write((char*)&l_Name, sizeof(string));
outFile.write((char*)&salary, sizeof(int));
outFile.write((char*)&vacation, sizeof(int));
outFile.write((char*)&meets, sizeof(int));
void Manager::LoadInfo(ifstream& inFile)
inFile.read((char*)&f_Name, sizeof(string));
inFile.read((char*)&l_Name, sizeof(string));
inFile.read((char*)&salary, sizeof(int));
inFile.read((char*)&vacation, sizeof(int));
inFile.read((char*)&meets, sizeof(int));
#ifndef RESEARCHER_H
#define RESEARCHER_H
#include <iostream>
#include <string>
#include <fstream>
#include "Employee.h"
using namespace std;
class Researcher : public Employee
public:
Researcher();
Researcher(string fName, string lName, int sal);
void BasicInfo();
void DisplayInfo();
void SaveInfo(ofstream& outFile);
void LoadInfo(ifstream& inFile);
~Researcher();
protected:
string TopicPhd, SchoolPhd;
;
#endif
Researcher::Researcher()
Researcher::Researcher(string fName, string lName, int sal)
f_Name = fName;
l_Name = lName;
salary = sal;
void Researcher::BasicInfo()
cout<<endl<<"Topic of PhD: ";
cin>>TopicPhd;
cout<<endl<<"School of PhD: ";
cin>>SchoolPhd;
void Researcher::DisplayInfo()
cout<<"RESEARCHER";
cout<<endl<<"Name: "<<f_Name<<" "<<l_Name;
cout<<endl<<"Salary: "<<salary<<endl;
cout<<"PhD: "<<TopicPhd<<"\nSchool: "<<SchoolPhd;
cout<<endl<<endl;
void Researcher::SaveInfo(ofstream& outFile)
outFile.write((char*)&f_Name, sizeof(string));
outFile.write((char*)&l_Name, sizeof(string));
outFile.write((char*)&salary, sizeof(int));
outFile.write((char*)&TopicPhd, sizeof(string));
outFile.write((char*)&SchoolPhd, sizeof(string));
void Researcher::LoadInfo(ifstream& inFile)
inFile.read((char*)&f_Name, sizeof(string));
inFile.read((char*)&l_Name, sizeof(string));
inFile.read((char*)&salary, sizeof(int));
inFile.read((char*)&TopicPhd, sizeof(string));
inFile.read((char*)&SchoolPhd, sizeof(string));
#ifndef ENGINEER_H
#define ENGINEER_H
#include <iostream>
#include <string>
#include <fstream>
#include "Employee.h"
using namespace std;
class Engineer : public Employee
public:
Engineer();
Engineer(string fName, string lName, int sal);
// void BasicInfo(bool knowCPP, int experience, string type);
void BasicInfo();
void DisplayInfo();
void SaveInfo(ofstream& outFile);
void LoadInfo(ifstream& inFile);
~Engineer();
protected:
bool isknowingCPP;
int exp;
string typeOfEng;
;
#endif
Engineer::Engineer()
Engineer::Engineer(string fName, string lName, int sal)
f_Name = fName;
l_Name = lName;
salary = sal;
void Engineer::BasicInfo()
cout<<endl<<"Knows C++(0/1): ";
cin>>isknowingCPP;
cout<<endl<<"Years of Experience: ";
cin>>exp;
cout<<endl<<"Field of Engineering: ";
cin>>typeOfEng;
void Engineer::DisplayInfo()
cout<<"TYPE: Engineer";
cout<<endl<<"Name: "<<f_Name<<" "<<l_Name;
cout<<endl<<"Salary: "<<salary<<endl;
cout<<"Knows C++: "<<isknowingCPP;
cout<<endl<<"Experience: "<<exp;
cout<<endl<<"Engineering: "<<typeOfEng;
cout<<endl<<endl;
Engineer::~Engineer()
void Engineer::SaveInfo(ofstream& outFile)
outFile.write((char*)&f_Name, sizeof(string));
outFile.write((char*)&l_Name, sizeof(string));
outFile.write((char*)&salary, sizeof(int));
outFile.write((char*)&isknowingCPP, sizeof(bool));
outFile.write((char*)&exp, sizeof(int));
outFile.write((char*)&typeOfEng, sizeof(string));
/*outFile<<"Engineer";
outFile<<endl<<"FirstName: "<<f_Name;
outFile<<endl<<"LastName: "<<l_Name;
outFile<<endl<<"Salary: "<<salary;
outFile<<endl<<"Knows C++: "<<isknowingCPP;
outFile<<endl<<"Experience: "<<exp;
outFile<<endl<<"Engineering: "<<typeOfEng;
outFile<<endl<<endl;*/
void Engineer::LoadInfo(ifstream& inFile)
inFile.read((char*)&f_Name, sizeof(string));
inFile.read((char*)&l_Name, sizeof(string));
inFile.read((char*)&salary, sizeof(int));
inFile.read((char*)&isknowingCPP, sizeof(bool));
inFile.read((char*)&exp, sizeof(int));
inFile.read((char*)&typeOfEng, sizeof(string));
#include <iostream>
#include <string>
#include <vector>
#include "Engineer.h"
#include "Manager.h"
#include "Researcher.h"
using namespace std;
void MenuControl(int id);
void AddEmployee(int type);
void DeleteEmployee(int id);
int empStrength;
bool quit = false;
vector<Employee*> emps;
int main()
/*Manager* man = new Manager("Shash", "Sharma", 30);
emps.push_back(man);
emps[0]->BasicInfo();*/
int optionID;
//delete emps[0];
while(!quit)
cout<<endl<<"1) Add Employee \n2) Delete Employee \n3)Display List \n4)Save Data \n5)Load Data \nAny other number to Quit: ";
cin>>optionID;
MenuControl(optionID);
void MenuControl(int id)
switch(id)
case 1:
int empType;
cout<<endl<<endl<<"Adding Employee..."<<endl;
cout<<endl<<"Please choose Employee category: "<<endl<<"1)Manager\n2)Researcher\n3)Engineer\nAny other number to exit: ";
cin>>empType;
AddEmployee(empType);
break;
case 2:
int deleteID;
cout<<endl<<"Deleting Employee..."<<endl;
cout<<endl<<"Enter Employee Code: ";
cin>>deleteID;
DeleteEmployee(deleteID);
break;
case 3:
if(emps.size()>0)
for(int i=0; i<emps.size(); i++)
emps[i]->DisplayInfo();
else
cout<<endl<<"No data available!"<<endl;
break;
case 4:
if(emps.size()>0)
ofstream outfile("EmployeeData.txt", ios_base::binary);
for(int i=0; i<emps.size(); i++)
emps[i]->SaveInfo(outfile);
outfile.close();
ofstream outfile02("Employees.dat", ios_base::binary);
outfile02.write((char*)&empStrength, sizeof(int));
cout<<endl<<"Employee Strength: "<<empStrength;
outfile02.close();
ofstream outfile03("EmployeeTypes.txt", ios_base::binary);
for(int i=0; i<emps.size(); i++)
//outfile03<<&emps[i]<<endl;
outfile03.write(reinterpret_cast<char*>(&emps[i]) , sizeof(Employee));
cout<<endl<<"Data Saved";
cout<<endl<<endl;
break;
case 5:
ifstream infile02("Employees.dat", ios_base::binary);
infile02.read((char*)&empStrength, sizeof(int));
cout<<endl<<"Employee Strength: "<<empStrength;
emps.resize(empStrength);
cout<<endl<<emps.size();
Employee* temp;
ifstream infile03("EmployeeTypes.txt", ios_base::binary);
// infile03.read(reinterpret_cast<char*>(&temp), sizeof(Employee));
for(int i=0; i<emps.size(); i++)
cout<<endl<<"BeforeSeg";
infile03.read(reinterpret_cast<char*>(temp), sizeof(Employee));
cout<<endl<<"SegError";
emps[i] = temp;
break;
default:
quit = true;
break;
void AddEmployee(int type)
string fName, lName;
int sal;
switch(type)
case 1:
//, holiday, meetings;
cout<<endl<<endl<<"First Name: ";
cin>>fName;
cout<<endl<<"Last Name: ";
cin>>lName;
cout<<endl<<"Salary: ";
cin>>sal;
Manager* man = new Manager(fName, lName, sal);
man->BasicInfo();
emps.push_back(man);
empStrength++;
break;
case 2:
cout<<endl<<endl<<"First Name: ";
cin>>fName;
cout<<endl<<"Last Name: ";
cin>>lName;
cout<<endl<<"Salary: ";
cin>>sal;
Researcher* res = new Researcher(fName, lName, sal);
res->BasicInfo();
emps.push_back(res);
empStrength++;
break;
case 3:
cout<<endl<<endl<<"First Name: ";
cin>>fName;
cout<<endl<<"Last Name: ";
cin>>lName;
cout<<endl<<"Salary: ";
cin>>sal;
Engineer* eng = new Engineer(fName, lName, sal);
eng->BasicInfo();
emps.push_back(eng);
empStrength++;
break;
default:
cout<<endl<<endl<<"No such Employee Type. Please put correct values"<<endl;
void DeleteEmployee(int id)
if(id<emps.size())
emps.erase(emps.begin() + id);
empStrength--;
else
cout<<endl<<"No such ID yet."<<endl;
我对 C++ 很陌生，所以请多多包涵:)
【问题讨论】：
【参考方案1】：一种方法是在您的员工类中定义一个类型变量，然后在每个派生构造函数中分配该变量，然后保存/加载此信息。
快速示例代码来举例说明我的建议：
// inside Employee.h
enum eEmployeeTypes
ET_NONE,
ET_MANAGER,
ET_RESEARCHER,
ET_ENGINEER
class Employee
...
protected:
eEmployeeTypes m_Type;
//employee cpp
Employee::Employee()
...
m_Type = ET_NONE
// Sample modified constructor for Manager
// manager.cpp
Manager::ManageR()
...
m_Type = ET_MANAGER;
现在是棘手的部分，因为您在加载时需要信息：
您应该首先将类型信息保存在文件中。
然后您应该为 Employee 创建一个 Factory 函数，它使用适当的构造函数并读取如下内容：
static Employee* CreateEmployeeFromFile(ifstream& file)
eEmployeeTypes type;
file.read((eEmployeeTypes*)&type, sizeof(eEmployeeTypes));
Employee* rez=null;
if (type == ET_MANAGER)
rez = new Manager();
rez.LoadInfo(file);
...
return rez;
【讨论】：
好的，我会测试你的方法。但是，如果我只是在数据中放置一个与每个 Employee 类型相关的 int ，而不是 Enum ，那也可以吗？例如：我将 Manager 设置为 1，Researcher 设置为 2 等等，然后在加载时从文件中读取，运行 switch 或 if 循环，就像你正在做的那样，并将每个元素实例化为相同？总之非常感谢。我会测试它并在一段时间内批准答案:) 枚举和整数实际上在 C++ 中是一回事，它只是帮助您获得连续递增的常量值。编译器可能会选择将枚举转换为 byte / short ，这就是为什么在使用枚举时使用 sizeof 枚举而不是直接假设它是一个 int 更安全。 哦，好的。因此，在将其保存为二进制文件时，我将其大小指定为 sizeof(eEmployeeTypes)? 如果你使用枚举，是的，这就是你想要的:)。您可以做的一个小技巧是强制枚举为 int ，因此如果您使用不同的编译器，以后就不会遇到不匹配的情况。这是技巧的链接（第二个答案是您要搜索的答案）：***.com/questions/4879286/… 抱歉回复晚了。我尝试以与您完全相同的方式进行操作，但它给出了一些错误，所以我只是简单地纠正了错误，我很高兴！非常感谢您的帮助！ :)以上是关于将对象的类类型保存到文件并在 C++ 中读回的主要内容，如果未能解决你的问题，请参考以下文章
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