Constructor Operator << Device and Test Dynamic Array

Question

#include iostream
#include cmath
#include fstream
#include cstdlib
#include string
using namespace std;
class Device {//Input and store Device Description and Serial Numbers
protected:
 static string  serial_number;
 static string device_description;
public:
 Device() {
     serial_number = ("6DCMQ32");
     device_description = ("TheDell");
 }
 Device(string s, string d) {
     serial_number = s;
    device_description = d;
 }
};
string Device::device_description;
string Device::serial_number;
class Test {//Input and store Test Description, recent day, and month; 
Calculate the next day
   protected:
      static string Test_Description;
      static int recent_month, recent_day, recent_year, new_month;
      static int nmonth, next_month, next_day, next_year, max_day;
   public:
   Test() {
        Test_Description = ("Virtual");
   }
   static void getMonth() {//Calculates the next/new month
    next_month = recent_month + nmonth;
    new_month = next_month % 12;
    if (next_month >= 12) {
        cout << "The next Date: " << new_month << " / ";
    }
    else {
        cout << "The next Date: " << next_month << " / ";
    }
}
static void getDay() {  //Calculates day of next month
          if (new_month == 4 || new_month == 6 || new_month == 9 || new_month == 11) {
         max_day = 30;
     }
     else if (new_month == 2) {
        max_day = 29;
     }
     else {
         max_day = 31;
     }
     if (recent_day > max_day) {
         cout << max_day << " / ";
     }
     else {
         cout << recent_day << " / ";
     }
 }
 static void getYear() {// Calculate the year of next month
     next_year = recent_year + next_month;
     if (next_year >= 12) {
         cout << recent_year + (next_month / 12) << endl;
     }
     else {
         cout << next_year << endl;
     }
 }
 static void getDate() {// Collects the output of each element of next date
     Test::getMonth(), Test::getDay(), Test::getYear();
 }
  };
 string Test::Test_Description;
 int Test::recent_month;
 int Test::recent_day;
 int Test::recent_year;
 int Test::new_month;
 int Test::nmonth;
 int Test::next_month;
 int Test::next_day;
 int Test::next_year;
 int Test::max_day;
 class Lab : public Device, public Test {
 protected:
     static int n;
  public:
 friend istream & operator>>(istream & in, Lab & lab) {// Inputs 
     cout << "Enter Device Desciption and Serial Number: ";
     getline(in, device_description);
     getline(in, serial_number);
     cout << "Enter Test Desciption: ";
     getline(in, Test_Description);
     cout << "Enter the Number of months: ";
     in >> nmonth;
     cout << "Enter the Most Recent Date(mm/dd/yyyy): ";
     in >> recent_month >> recent_day >> recent_year;
     return in;
   }
   friend ostream & operator<<(ostream & out, Lab & lab) {//Outputs 
    everything in Device Class
     out << Lab::device_description << endl;
     out << Lab::serial_number << endl;
     out << Lab::Test_Description << endl;
     getDate();
     return out;
    }
    static void getN() {
     cout << "Enter the number of devices: ";
     cin >> n;
    }
    static void getWrite() {        
     Lab *obj = new Lab[n];
       if (obj == 0) {
         cout << "Memory Error";
         exit(1);
       }
     for (int i = 0; i<n; i++) {
         cin >> obj[i];
         cout << endl;
     }
     ofstream myfile("Device.txt");
     myfile.write((char *)obj, n * sizeof(Lab));
     delete[] obj;      
   }
   static void getRead() {
     ifstream file2("Device.txt");
     Lab *obj2 = new Lab[n];
     if (obj2 == 0) {
         cout << "Memory Error";
         exit(1);
     }
     file2.read((char *)obj2, n * sizeof(Lab));
     for (int i = 0; i < n; i++) {
         cout << obj2[i];
         cout << endl;
     }
     delete[] obj2;
 }
 /*void getSearch(){

 }*/
};
int Lab::n;
void main() {
   Lab L;
   L.getN();
   L.getWrite();
   L.getRead();
   system("pause");
}

The Output I get is TheDell 6DCMQ32, Virtual when I entered my inputs. The date is correct the only problem is the Device Description, Serial Number, and Test Device.

Problem with Operator << in File i/o reading where it outputs the values in the Constructor

Purpose: is to enter the number of months for the next test date of device with input of serial number, Device Description, Test Description, recent date, and the number of months of two tests. At the end the program must be searched by having the user to input the serial number and the next date, if these two are valid everything in the device is listed out.

Answer 1

Short of writing your application, I will do my best to give you some direction.

#include <iostream> // Note the '<' and '>' this is to specify is a language provided include
// More includes with the same issue...
using namespace std; // this is general considered bad=practice see https://stackoverflow.com/a/1452738/8480874 for details

//Input and store Device Description and Serial Numbers
class Device
{                                        // Notice the white space makes it easier to read...
protected:
   //static string  serial_number; // declaring this static means _EVERY_ device will have the same serial number
   //static string device_description;  // same as above
   string serialNumber;
   string deviceDesc;
public:
   Device() : serialNumber("6DCMQ32"), deviceDesc("TheDell")
   {
     //serial_number = ("6DCMQ32");      // Not the best place for initialization
     //device_description = ("TheDell"); // Not the best place for initialization
   }
   //Device(string s, string d)       // you never actually use this
   //{
   //  serial_number = s;
   //  device_description = d;
   //}
};
//string Device::device_description; // This is a sign that you variable will be shared between everyone - not required if you remove the static
//string Device::serial_number;      // This is a sign that you variable will be shared between everyone - not required if you remove the static



// This suffers from the same probles as the `class device` above
class Test
{
  // Lots of stuff was here just trying to short the answer....
  // Mostly has the same culprits mentions for the device

     // This is one of the fucntions which gets called when you are trying to "save" the info to a file
     static void getMonth(/* ostream & out */) // you need this as a paramater
     {
        next_month = recent_month + nmonth;
        new_month = next_month % 12;

        if (next_month >= 12)
        {
           // This function has no idea is needs to redirect the out put to a file...
           // its only outputting to the standard console
           cout << "The next Date: " << new_month << " / ";
        }
        else
        {
           //cout << "The next Date: " << next_month << " / ";

           // using the new parameter in comments
           // you can now save to your file
           out << /*"The next Date: " <<*/ next_month << " / "; // no I comment out your extra message since you file reading does not look for that
        }
     }
  };


  // Again we have the same general misuse of C++ ( please keep learning! hopefully I am point you in the right direction )
 class Lab : public Device, public Test
 {
 protected:
     static int n;
  public:
 friend istream & operator>>(istream & in, Lab & lab)
 {
    // Inputs 
     cout << "Enter Device Desciption and Serial Number: ";
     getline(in, device_description);
     getline(in, serial_number);
     cout << "Enter Test Desciption: ";
     getline(in, Test_Description);
     cout << "Enter the Number of months: ";
     in >> nmonth;
     cout << "Enter the Most Recent Date(mm/dd/yyyy): ";
     in >> recent_month >> recent_day >> recent_year;
     return in;
   }

   friend ostream & operator<<(ostream & out, Lab & lab) {//Outputs 
    everything in Device Class
     out << Lab::device_description << endl;
     out << Lab::serial_number << endl;
     out << Lab::Test_Description << endl;

     // Here you should pass the output pipe
     getDate(/* out */);

     return out;
    }

    static void getN() {
     cout << "Enter the number of devices: ";
     cin >> n;
    }


    static void getWrite()
    {
       // there's no real need to be using a pointer or memory allocation
       //Lab *obj = new Lab[n];

       // you can simply use
       Lab obj[n];

       //if (obj == 0)
       //{
       //  cout << "Memory Error";
       //  exit(1);
       //}

      for (int i = 0; i < n; i++)
      {
         cin >> obj[i];
         cout << endl;
      }

      ofstream myfile("Device.txt");
      //myfile.write((char *)obj, n * sizeof(Lab)); // I've never tried writting an object's memory as a char* to file

      // usually I like to generate a human readable output 
      std::string objBuffer = obj.getSaveBuffer(); // you will need to implement this `getSaveBuffer()` functions
      myfile << objBuffer; // This can save lots of different value types for you! see http://www.cplusplus.com/reference/ostream/ostream/operator%3C%3C/

      //delete[] obj; // since there is no more new; we dont need a delete!
   }

   // The logic of what you read suffers the same general issues as the write.
   // Also what/how you read is very far from the save so I can't venture into any solutions
   // I'm hoping this will kick start you to figuring it out on your own =)
   static void getRead() {
     ifstream file2("Device.txt");
     Lab *obj2 = new Lab[n];
     if (obj2 == 0) {
         cout << "Memory Error";
         exit(1);
     }

     file2.read((char *)obj2, n * sizeof(Lab));
     for (int i = 0; i < n; i++) {
         cout << obj2[i];
         cout << endl;
     }
     delete[] obj2;
 }
 /*void getSearch(){

 }*/
};
int Lab::n;


// A program that runs should always return a numeric result indicating success or failure
//void main() {
int main()
{

   Lab L;    // Since everything in all your classes is static this didnt really add anything
             // you done need an object if the object contains nothing

   L.getN();
   L.getWrite();
   L.getRead();

   system("pause"); // this is also bad practice, see https://stackoverflow.com/a/1107717/8480874
   // I personally like `getchar()` because it's easy and quick

}