oop.cpp

#include <iostream>
#include <fstream>
#include <string>

// Abstract class for abstraction
class Person {
protected:
    std::string name;
    int age;

public:
    // Pure virtual function to ensure derived class implements it
    virtual void getDetails() = 0;
    virtual void displayDetails() const = 0;
};

// Derived class implementing abstraction and encapsulation
class User : public Person {
private:
    std::string occupation;
    static const std::string databaseFile; // File to store data

public:
    // Constructor
    User() : occupation("Unknown") {}

    // Function to get user input (Override base class)
    void getDetails() override {
        std::cout << "Enter name: ";
        std::cin >> name;
        std::cout << "Enter age: ";
        std::cin >> age;
        std::cout << "Enter occupation: ";
        std::cin >> occupation;
    }

    // Function to display user details (Override base class)
    void displayDetails() const override {
        std::cout << "Name: " << name << ", Age: " << age << ", Occupation: " << occupation << std::endl;
    }

    // Function to write user data to file (Persistence)
    void writeToFile() {
        std::ofstream outFile(databaseFile, std::ios::app); // Append mode to avoid overwriting
        if (outFile.is_open()) {
            outFile << name << " " << age << " " << occupation << std::endl; // Save details
            outFile.close();
        } else {
            std::cout << "Error opening file for writing." << std::endl;
        }
    }

    // Static function to read and display all users from file
    static void readFromFile() {
        std::ifstream inFile(databaseFile);
        std::string file_name, file_occupation;
        int file_age;
        if (inFile.is_open()) {
            while (inFile >> file_name >> file_age >> file_occupation) {
                std::cout << "Name: " << file_name << ", Age: " << file_age << ", Occupation: " << file_occupation << std::endl;
            }
            inFile.close();
        } else {
            std::cout << "Error opening file for reading." << std::endl;
        }
    }

    // Static function to edit a user by name
    static void editUserDetails(const std::string &searchName, const std::string &newOccupation) {
        std::ifstream inFile(databaseFile);
        std::ofstream tempFile("temp.txt"); // Temporary file for edits

        std::string file_name, file_occupation;
        int file_age;
        bool found = false;

        if (inFile.is_open() && tempFile.is_open()) {
            while (inFile >> file_name >> file_age >> file_occupation) {
                if (file_name == searchName) {
                    file_occupation = newOccupation; // Update occupation
                    found = true;
                }
                tempFile << file_name << " " << file_age << " " << file_occupation << std::endl;
            }
            inFile.close();
            tempFile.close();

            std::remove(databaseFile.c_str());
            std::rename("temp.txt", databaseFile.c_str());

            if (found) {
                std::cout << "User updated successfully.\n";
            } else {
                std::cout << "User not found.\n";
            }
        } else {
            std::cout << "Error opening files for editing.\n";
        }
    }

    // Static function to delete a user by name
    static void deleteUser(const std::string &searchName) {
        std::ifstream inFile(databaseFile);
        std::ofstream tempFile("temp.txt"); // Temporary file for edits

        std::string file_name, file_occupation;
        int file_age;
        bool found = false;

        if (inFile.is_open() && tempFile.is_open()) {
            while (inFile >> file_name >> file_age >> file_occupation) {
                if (file_name != searchName) {
                    tempFile << file_name << " " << file_age << " " << file_occupation << std::endl;
                } else {
                    found = true;
                }
            }
            inFile.close();
            tempFile.close();

            std::remove(databaseFile.c_str());
            std::rename("temp.txt", databaseFile.c_str());

            if (found) {
                std::cout << "User deleted successfully.\n";
            } else {
                std::cout << "User not found.\n";
            }
        } else {
            std::cout << "Error opening files for deletion.\n";
        }
    }
};

// Initialize static variable
const std::string User::databaseFile = "user_database.txt";

// Main menu-driven program
int main() {
    User user;
    int choice;
    std::string searchName, newOccupation;

    do {
        std::cout << "\n*** User Management System ***\n";
        std::cout << "1. Add User\n";
        std::cout << "2. View All Users\n";
        std::cout << "3. Edit User\n";
        std::cout << "4. Delete User\n";
        std::cout << "5. Exit\n";
        std::cout << "Enter your choice: ";
        std::cin >> choice;

        switch (choice) {
            case 1:
                user.getDetails();   // Get user input
                user.writeToFile();  // Write data to file
                break;
            case 2:
                User::readFromFile();  // Display all users from file
                break;
            case 3:
                std::cout << "Enter the name of the user to edit: ";
                std::cin >> searchName;
                std::cout << "Enter new occupation: ";
                std::cin >> newOccupation;
                User::editUserDetails(searchName, newOccupation);  // Edit user by name
                break;
            case 4:
                std::cout << "Enter the name of the user to delete: ";
                std::cin >> searchName;
                User::deleteUser(searchName);  // Delete user by name
                break;
            case 5:
                std::cout << "Exiting...\n";
                break;
            default:
                std::cout << "Invalid choice, try again.\n";
                break;
        }
    } while (choice != 5);

    return 0;
}