I need help with my homework assignment

[gieenet]

I am working on a program for my Data Structures and Algorithms in C++ class.

Define function isNull () & writeNullToFile () in classes Personal and Student. Then define function remove ( ) in Database (very similar to modify ()). which locates the position of the record to be deleted and overwrites it with the null record. After a session in finished, a Database destructor should be invoked, which copies nonnull records to a new data file, deletes the old data file, and renames the new data file with the name of the old file.


//***********************************personal.h**************************************
#include <iostream>
#include <fstream>
#include <cstring>
#include <stdio.h>

using namespace std;

#ifndef PERSONAL
#define PERSONAL

class Personal {
public:
Personal();
Personal(char*,char*,char*,int,long);
void writeToFile(fstream&) const;
void writeNullToFile(fstream&) const;
void readFromFile(fstream&);
void readKey();
void isNull();
int size() const {
return 9 + nameLen + cityLen + sizeof(year) + sizeof(salary);
}
bool operator==(const Personal& pr) const {
return strncmp(pr.SSN,SSN,9) == 0;
}
protected:
const int nameLen, cityLen;
char SSN[10], *name, *city;
int year;
long salary;
ostream& writeLegibly(ostream&);
friend ostream& operator<<(ostream& out, Personal& pr) {
return pr.writeLegibly(out);
}
istream& readFromConsole(istream&);
friend istream& operator>>(istream& in, Personal& pr) {
return pr.readFromConsole(in);
}
};

#endif

//************************personal.cpp***********************

#include "personal.h"

Personal::Personal() : nameLen(10), cityLen(10) {
name = new char[nameLen+1];
city = new char[cityLen+1];
}

Personal::Personal(char *ssn, char *n, char *c, int y, long s) :
nameLen(10), cityLen(10) {
name = new char[nameLen+1];
city = new char[cityLen+1];
strcpy(SSN,ssn);
strcpy(name,n);
strcpy(city,c);
year = y;
salary = s;
}

void Personal::writeToFile(fstream& out) const {
out.write(SSN,9);
out.write(name,nameLen);
out.write(city,cityLen);
out.write(reinterpret_cast<const char*>(&year),sizeof(int));
out.write(reinterpret_cast<const char*>(&salary),sizeof(int));
}

void Personal::readFromFile(fstream& in) {
in.read(SSN,9);
in.read(name,nameLen);
in.read(city,cityLen);
in.read(reinterpret_cast<char*>(&year),sizeof(int));
in.read(reinterpret_cast<char*>(&salary),sizeof(int));
}

void Personal::readKey() {
char s[80];
cout << "Enter SSN: ";
cin.getline(s,80);
strncpy(SSN,s,9);
}

ostream& Personal::writeLegibly(ostream& out) {
SSN[9] = name[nameLen] = city[cityLen] = '\0';
out << "SSN = " << SSN << ", name = " << name
<< ", city = " << city << ", year = " << year
<< ", salary = " << salary;
return out;
}

istream& Personal::readFromConsole(istream& in) {
char s[80];
cout << "SSN: ";
in.getline(s,80);
strncpy(SSN,s,9);
cout << "Name: ";
in.getline(s,80);
strncpy(name,s,nameLen);
cout << "City: ";
in.getline(s,80);
strncpy(city,s,cityLen);
cout << "Birthyear: ";
in >> year;
cout << "Salary: ";
in >> salary;
in.getline(s,80); // get '\n'
return in;
}
//*****************************student.h***************************************

#ifndef STUDENT
#define STUDENT

#include "personal.h"

class Student : public Personal {
public:
Student();
Student(char*,char*,char*,int,long,char*);
void writeToFile(fstream&) const;
void writeNullToFile(fstream&) const;
void readFromFile(fstream&);
void isNull();
int size() const {
return Personal::size() + majorLen;
}
protected:
char *major;
const int majorLen;
ostream& writeLegibly(ostream&);
friend ostream& operator<<(ostream& out, Student& sr) {
return sr.writeLegibly(out);
}
istream& readFromConsole(istream&);
friend istream& operator>>(istream& in, Student& sr) {
return sr.readFromConsole(in);
}
};

#endif

//**********************************student.cpp*************************************

#include "student.h"

Student::Student() : majorLen(10) {
Personal();
major = new char[majorLen+1];
}

Student::Student(char *ssn, char *n, char *c, int y, long s, char *m) :
majorLen(11) {
Personal(ssn,n,c,y,s);
major = new char[majorLen+1];
strcpy(major,m);
}

void Student::writeToFile(fstream& out) const {
Personal::writeToFile(out);
out.write(major,majorLen);
}

void Student::readFromFile(fstream& in) {
Personal::readFromFile(in);
in.read(major,majorLen);
}

ostream& Student::writeLegibly(ostream& out) {
Personal::writeLegibly(out);
major[majorLen] = '\0';
out << ", major = " << major;
return out;
}

istream& Student::readFromConsole(istream& in) {
Personal::readFromConsole(in);
char s[80];
cout << "Major: ";
in.getline(s,80);
strncpy(major,s,9);
return in;
}
//*************************************database.h************************************

#ifndef DATABASE
#define DATABASE

template<class T>
class Database {
public:
Database();
void run();
private:
fstream database;
char fName[20];
ostream& print(ostream&);
void add(T&);
bool find(const T&);
void modify(const T&);
void remove(const T&);
friend ostream& operator<<(ostream& out, Database& db) {
return db.print(out);
}
};

#endif

//*********************************database.cpp*************************************

#include "personal.h"
#include "student.h"
#include "database.h"

template<class T>
Database<T>::Database() {
}

template<class T>
void Database<T>::add(T& d) {
database.open(fName,ios::in|ios::out|ios::binary);
database.clear();
database.seekp(0,ios::end);
d.writeToFile(database);
database.close();
}

template<class T>
void Database<T>::modify(const T& d) {
T tmp;
database.open(fName,ios::in|ios::out|ios::binary);
database.clear();
while (!database.eof()) {
tmp.readFromFile(database);
if (tmp == d) { // overloaded ==
cin >> tmp; // overloaded >>
database.seekp(-d.size(),ios::cur);
tmp.writeToFile(database);
database.close();
return;
}

}
database.close();
cout << "The record to be modified is not in the database\n";
}

template<class T>
void Database<T>::remove(const T& d) {
T tmp;
database.open(fName,ios::in|ios::out|ios::binary);
database.clear();
while (!database.eof()) {
tmp.readFromFile(database);
if (tmp == d) { // overloaded ==
cin >> tmp; // overloaded >>
database.seekp(-d.size(),ios::cur);
tmp.writeNullToFile(database);
database.close();
return;
}

}
database.close();
cout << "The record to be deleted is not in the database\n";
}


template<class T>
bool Database<T>::find(const T& d) {
T tmp;
database.open(fName,ios::in|ios::binary);
database.clear();
while (!database.eof()) {
tmp.readFromFile(database);
if (tmp == d) { // overloaded ==
database.close();
return true;
}
}
database.close();
return false;
}

template<class T>
ostream& Database<T>::print(ostream& out) {
T tmp;
database.open(fName,ios::in|ios::binary);
database.clear();
while (true) {
tmp.readFromFile(database);
if (database.eof())
break;
out << tmp << endl; // overloaded <<
}
database.close();
return out;
}

template<class T>
void Database<T>::run() {
cout << "File name: ";
cin >> fName;
cin.ignore(); // skip '\n';
database.open(fName,ios::in);
if (database.fail())
database.open(fName,ios::out);
database.close();
char option[5];
T rec;
cout << "1. Add 2. Find 3. Modify a record; 4. Delete a Record 5. Exit\n";
cout << "Enter an option: ";
while (cin.getline(option,6)) {
if (*option == '1') {
cin >> rec; // overloaded >>
add(rec);
}
else if (*option == '2') {
rec.readKey();
cout << "The record is ";
if (find(rec) == false)
cout << "not ";
cout << "in the database\n";
}
else if (*option == '3') {
rec.readKey();
modify(rec);
}
else if (*option == '4') {
rec.readKey();
remove(rec);

}

else if (*option != '5')
cout << "Wrong option\n";
else return;
cout << *this; // overloaded <<
cout << "Enter an option: ";
}
}

int main() {
Database<Personal>().run();
// Database<Student>().run();
return 0;
}

[gieenet]

I am fairly new to programming so I will not be offended if you expert programmers talk down to me. I have my C++ for dummies for all the questions that is over my head. The steps I have completed so far follows. I will appreciate any guidance in the right direction for the other steps. Also I am getting the following error.

error LNK2019: unresolved external symbol "public: void __thiscall Personal::writeNullToFile(class std::basic_fstream<char,struct std::char_traits<char> > &)const " (?writeNullToFile@Personal@@QBEXAAV?$basic_fstream@DU?$char_traits@D@std@@@std@@@Z) referenced in function "private: void __thiscall Database<class Personal>::remove(class Personal const &)" (?remove@?$Database@VPersonal@@@@AAEXABVPersonal@@@Z)

Thanks in advance



1. Add an option to remove file form database:


else if (*option == '4') {
rec.readKey();
remove(rec);
}


2. Define Function isNull( ) in class Personal to determine the record is null.

class Personal {
public:
Personal();
Personal(char*,char*,char*,int,long);
void writeToFile(fstream&) const;
void readFromFile(fstream&);
void readKey();
void isNull();
int size() const {
return 9 + nameLen + cityLen + sizeof(year) + sizeof(salary);
}

3. Define Function isNull( ) in class Student to determine the record is null.

class Student : public Personal {
public:
Student();
Student(char*,char*,char*,int,long,char*);
void writeToFile(fstream&) const;
void readFromFile(fstream&);
void isNull();
int size() const {
return Personal::size() + majorLen;
}

4. Define Function writeToFile ( ) in class Personal to overwrite a record to be deleted by a null record.

class Student : public Personal {
public:
Student();
Student(char*,char*,char*,int,long,char*);
void writeToFile(fstream&) const;
void writeNullToFile(fstream&) const;
void readFromFile(fstream&);
void isNull();
int size() const {
return Personal::size() + majorLen;
}

5. Define Function writeToFile ( ) in class Student to overwrite a record to be deleted by a null record.

class Student : public Personal {
public:
Student();
Student(char*,char*,char*,int,long,char*);
void writeToFile(fstream&) const;
void writeNullToFile(fstream&) const;
void readFromFile(fstream&);
void isNull();
int size() const {
return Personal::size() + majorLen;
}


6. Define Function remove( ) in database which locates the position of a record to be deleted and overwrites it with the null record.

class Database {
public:
Database();
void run();
private:
fstream database;
char fName[20];
ostream& print(ostream&);
void add(T&);
bool find(const T&);
void modify(const T&);
void remove(const T&);
friend ostream& operator<<(ostream& out, Database& db) {
return db.print(out);
}

7. Deleting record form database

template<class T>
void Database<T>::remove(const T& d) {
T tmp;
database.open(fName,ios::in|ios::out|ios::binary);
database.clear();
while (!database.eof()) {
tmp.readFromFile(database);
if (tmp == d) { // overloaded ==
cin >> tmp; // overloaded >>
database.seekp(-d.size(),ios::cur);
tmp.writeNullToFile(database);
database.close();
return;
}

}
database.close();
cout << "The record to be deleted is not in the database\n";
8. After a session in finished, a Database destructor should be involked, which copies nonnull records to a new data file, deletes the old data file, and renames the new data file with the name of the old file.