如何使用默认的类构造函数创建多个新的类对象？
对于一个项目，我不得不编写一个将三个类对象写入文件的程序。我已经完成了...下一部分是能够使用readData函数将数据读回三个单独的类对象，然后显示数据。我完全迷失了如何做到这一点所以我在readData函数中没有任何代码。
以下是对象在写入文件时的外观示例。
employee name(21, "first last", "45 East State", "661-9000", 30, 12.00);
以下是我的代码的大部分，雇员类是相当基本的，但这里是默认的类构造函数。
employee::employee ();
employee::employee(int locEmpNumber, string locName, string locaddress, string locphone, double locHrWorked, double locHrWage)
#include "employee.h"
#include <string>
#include <iomanip>
#include <iostream>
#include <fstream>
using namespace std;
void writeData (const employee& e);
void readData (const employee& e);
void printCheck (const employee& e);
int main( )
{
//Declarations
const int ONE = 1;
const int TWO = 2;
int userInput;
cout << "This program has two options:" << endl;
cout << "1 - Create a data files called 'EmployeeInfo.txt', or" << endl;
cout << "2 - Read data from a file and print paychecks." << endl;
cout << "Please enter (1) to create a file or (2) to print checks: ";
cin >> userInput;
if (userInput == ONE)
{
//Create employee objects:
employee joe(37, "Joe Brown", "123 Main St.", "123-6788", 45, 10.00);
employee sam(21, "Sam Jones", "45 East State", "661-9000", 30, 12.00);
employee mary(15, "Mary Smith", "12 High Street", "401-8900", 40, 15.00);
ofstream empFile ("EmployeeInfo.txt");
//Employee objects to write themselves out to the file.
writeData(joe);
writeData(sam);
writeData(mary);
//Close the file.
empFile.close();
//Print an message that creation of the file is complete.
system("CLS");
cout << "\nCreation of 'EmployeeInfo.txt' has completed.\n";
cout << "\nYou can now run option 2.\n";
//Exit.
system("PAUSE");
return 0;
}
else if (userInput == TWO)
{
//Create three new Employee objects, using the default Employee constructor.
//Open the file that you just saved.
//Have each object read itself in from the file.
//Call the printCheck( ) function for each of the three new objects, just as you did in the previous project.
}
else
{
system("CLS");
cout << "Incorrect entry.... Please try again and follow directions closely! \n" << endl;
system("PAUSE");
return 0;
}
}
void writeData(const employee& e)
{
fstream empFile;
empFile.open ("EmployeeInfo.txt", ios::app);
empFile << e.getEmpNumber() << "\n";
empFile << e.getName() << "\n";
empFile << e.getAddress() << "\n";
empFile << e.getPhone() << "\n";
empFile << e.getHrWorked() << "\n";
empFile << e.getHrWage() << "\n";
}
void readData(const employee& e)
{
fstream empFile;
empFile.open ("EmployeeInfo.txt", ios::in);
if(empFile.fail())
{
cout << "File could not be open. Please try option 1 then option 2.\n" << endl;
return;
}
}
答案 0 :(得分：0)
很高兴看到你已经努力解决问题。但是，您在问题中列出的内容与代码中的某些注释之间存在不匹配。我似乎很清楚，你的简要说明的一个关键部分是雇员对象本身需要能够将自己写入文件并从文件中读回来。
您编写的代码会将对象的内容写入文件，而不是让对象将自身写入文件。看起来我可能会分裂这个，但这是面向对象编程的本质。在这里填充对象本身的功能是真正的目标。
我在下面提供了一些代码来帮助您。希望这对你来说很有意义。
class employee
{
private:
int _locEmpNumber;
std::string _locName;
std::string _locAddress;
std::string _locPhone;
double _locHrWorked;
double _locHrWage;
public:
employee();
employee(int locEmpNumber, std::string locName, std::string locAddress, std::string locPhone, double locHrWorked, double locHrWage);
//object should be able to save itself as per your project brief.
void writeData(std::ofstream &empFile);
//object should be able to read itself from file as per your project brief
void readData(std::ifstream &empFile);
};
employee::employee()
{
_locEmpNumber = 0;
_locHrWorked = _locHrWage = 0;
}
employee::employee(int locEmpNumber, std::string locName, std::string locAddress, std::string locPhone, double locHrWorked, double locHrWage)
{
_locEmpNumber = locEmpNumber;
_locName = locName;
_locAddress = locAddress;
_locPhone = locPhone;
_locHrWorked = locHrWorked;
_locHrWage = locHrWage;
}
//
//From what I can glean from your brief ...
//Employee objects to write themselves out to the file!!!
void employee::writeData(std::ofstream &empFile)
{
empFile << _locEmpNumber << std::endl;
empFile << _locName << std::endl;
empFile << _locAddress<< std::endl;
empFile << _locPhone << std::endl;
empFile << _locHrWorked << std::endl;
empFile << _locHrWage << std::endl;
}
//
//Again, from what I can glean from your brief ...
//Have each object read itself in from the file!!!
void employee::readData(std::ifstream &empFile)
{
//Normally you would have error handling in a method like this and
//would either return a response that indicates that the operation
//succeded or failed. You might alternatively use exception handling
//or indeed a combination of both.
//
//Normally you would reset all members to initial / empty values before
//reading values into them from your file. In this case we will omit that
//for the purposes of simplicity. The main reason you would reset members
//is to ensure that when reusing an object you don't end up with partial
//data from the current "read" operation mixed with partial data that
//was already in the object before you started reading.
std::string inputStr;
std::getline(empFile, inputStr);
_locEmpNumber = atoi(inputStr.c_str());
std::getline(empFile, _locName);
std::getline(empFile, _locAddress);
std::getline(empFile, _locPhone);
std::getline(empFile, inputStr);
_locHrWorked = atof(inputStr.c_str());
std::getline(empFile, inputStr);
_locHrWage = atof(inputStr.c_str());
}
int main(int argc, char* argv[])
{
//Declarations
const int ONE = 1;
const int TWO = 2;
int userInput;
std::cout << "This program has two options:" << std::endl;
std::cout << "1 - Create a data files called 'EmployeeInfo.txt', or" << std::endl;
std::cout << "2 - Read data from a file and print paychecks." << std::endl;
std::cout << "Please enter (1) to create a file or (2) to print checks: ";
std::cin >> userInput;
if (userInput == ONE)
{
//Create employee objects:
employee joe(37, "Joe Brown", "123 Main St.", "123-6788", 45, 10.00);
employee sam(21, "Sam Jones", "45 East State", "661-9000", 30, 12.00);
employee mary(15, "Mary Smith", "12 High Street", "401-8900", 40, 15.00);
std::ofstream empFile ("EmployeeInfo.txt");
//Employee objects to write themselves out to the file.
joe.writeData(empFile);
sam.writeData(empFile);
mary.writeData(empFile);
// writeData(joe);
// writeData(sam);
// writeData(mary);
//Close the file.
empFile.close();
//Print an message that creation of the file is complete.
system("CLS");
std::cout << "\nCreation of 'EmployeeInfo.txt' has completed.\n";
std::cout << "\nYou can now run option 2.\n";
//Exit.
system("PAUSE");
return 0;
}
else if (userInput == TWO)
{
//Create three new Employee objects, using the default Employee constructor.
employee joe;
employee sam;
employee mary;
//Open the file that you just saved.
std::ifstream empFile("EmployeeInfo.txt");
//Have each object read itself in from the file.
joe.readData(empFile);
sam.readData(empFile);
mary.readData(empFile);
empFile.close();
//Call the printCheck( ) function for each of the three new objects, just as you did in the previous project.
//I'll leave it to you to add this yourself.
}
else
{
system("CLS");
std::cout << "Incorrect entry.... Please try again and follow directions closely! \n" << std::endl;
system("PAUSE");
return 0;
}
return 0;
}