Need Help with Abstract Factory Pattern/Linked List Exercise

[Debie Ade]

I am a newbie to C++ programming and currently working on a program using Abstract Factory design pattern and linked list to store the objects and display them.
The user is expected to select whether the entry is for a management staff or Junior staff then save the parameters in the linked list and display them too.

I have created the abstract factories and the linked list but I am stuck on how to save the objects and display them with the linked list.

I need help with how to pass the staff object to the linked list and display them.

Thank you.

I have five files - Staff.h, Staff.cpp, StaffList.h, StaffList.cpp and StaffMain.cpp

The codes are below

Staff.h

#pragma once #include<string> class Staff { private: std::string Name; std::string Address; int age; public: Staff() //default constructor is assigned default values { Name = ""; Address = ""; age = 0; } Staff(std::string zName, std::string zAddress, int zage) //parameterized constructor is initialized to the values of the private members. { Name = zName; Address = zAddress; age = zage; } virtual void display() = 0; virtual void input() = 0; }; class JuniorStaff : public Staff { private: std::string Name; std::string Address; int age; std::string staffLevel; public: JuniorStaff() //default constructor is assigned default values { Name = ""; Address = ""; age = 0; staffLevel = ""; } void input(); void display(); }; class MgtStaff : public Staff { //declaring a derived class "FamilyCar" with base class "Car" private: std::string Name; std::string Address; int age; std::string mgrLevel; public: MgtStaff() //default constructor is assigned default values { Name = ""; Address = ""; age = 0; mgrLevel = ""; } void input(); void display(); }; class StaffFactory { public: virtual Staff* staffDetails() = 0; }; class JuniorStaffFactory :public StaffFactory { public: Staff* staffDetails() { return new JuniorStaff(); } }; class MgtStaffFactory :public StaffFactory { public: Staff* staffDetails() { return new MgtStaff(); } };

Staff.cpp


#include<iostream> #include<string> #include"Staff.h" using namespace std; void Staff::input() { } void Staff::display() { cout << "The staff name is " << Name << endl; cout << "The address of staff is " << Address << endl; cout << "The staff age is " << age << "years" << endl; } void JuniorStaff::input() { cout << "Enter staff name: " << endl; cin.ignore(); getline(cin, Name); cout << "Enter address of staff: " << endl; cin.ignore(); getline(cin, Address); cout << "Enter staff age: " << endl; cin.ignore(); cin >> age; cout << "Enter staff level: " << endl; cin.ignore(); getline(cin, staffLevel); } void JuniorStaff::display() { cout << "The staff name is " << Name << endl; cout << "The address of staff is " << Address << endl; cout << "The staff age is " << age << "years" << endl; cout << "The staff level is " << staffLevel << endl; } void MgtStaff::input() { cout << "Enter staff name: " << endl; cin.ignore(); getline(cin, Name); cout << "Enter address of staff: " << endl; cin.ignore(); getline(cin, Address); cout << "Enter staff age: " << endl; cin.ignore(); cin >> age; cout << "Enter Management level: " << endl; cin.ignore(); getline(cin, mgrLevel); mgrLevel = mgrLevel; } void MgtStaff::display() { cout << "The staff name is " << Name << endl; cout << "The address of staff is " << Address << endl; cout << "The staff age is " << age << "years" << endl; cout << "The Manager level is " << mgrLevel << endl; }

StaffList.h

#pragma once #include"Staff.h" class List { private: class Node { friend class List; StaffFactory* newstaff; Node* next; public: Node() { this->newstaff = NULL; this->next = NULL; }; Node(StaffFactory* c, Node* n) { this->newstaff = c; this->next = n; } }; List::Node* head; List::Node* curr; public: //this is where the functions go List(); void AddNode(StaffFactory* c); void PrintList(); };


StaffList.cpp

#include<iostream> #include<string> #include"StaffList.h" #include"Staff.h" using namespace std; List::List() //default constructor for List { head = NULL; curr = NULL; } void List::AddNode(StaffFactory* c) //function to add node { List::Node* n = new List::Node; n->next = NULL; n->newstaff = c; if (head == NULL) //check if the list is empty { head = n; } else { curr = head; //start of the list and iterates till next points to end of the list while (curr->next != NULL) { curr = curr->next; } curr->next = n; } } void List::PrintList() //print nodes in the list { curr = head; while (curr != NULL) //each node is printed till current pointer gets to end of the list { curr->newstaff->staffDetails(); curr = curr->next; } }

StaffMain.cpp

#include <iostream> #include<string> #include"Staff.h" #include"StaffList.h" using namespace std; int main() { List stafflist; int choice; cout << "Select type of staff: " << endl; cout << "1: Junior Staff" << endl; cout << "2: Management Staff" << endl; cout << "Selection: "; cin >> choice; cout << endl; StaffFactory* newStaff; switch (choice) { case 1: newStaff = new JuniorStaffFactory; break; case 2: newStaff = new MgtStaffFactory; break; default: cout << "Invalid selection!!!" << endl; newStaff = NULL; break; } if (newStaff != NULL) { Staff* c = newStaff->staffDetails(); c->input(); c->display(); stafflist.AddNode(newStaff); Staff* d = newStaff->staffDetails(); d->input(); stafflist.AddNode(newStaff); stafflist.PrintList(); } }

[Salil Wadnerkar]

  if (newStaff != NULL)
    {
        Staff* c = newStaff->staffDetails();
        c->input();
        c->display();
        stafflist.AddNode(newStaff);
 
        Staff* d = newStaff->staffDetails();
        d->input();
 
        stafflist.AddNode(newStaff);
 
        stafflist.PrintList();
    }

Why are you creating two instances of Staff - c and d?
Also, fix your naming so that someone reading the code can gets a better picture of the logic. Yourt newStaff should be renamed to staffFactory. And staffDetails() method should be renamed to createStaff. And c and d variables - you don't need d, but say, c can be renamed to newStaff.

[Debie Ade]

I have updated the main function as below:

if (newStaffFactory != NULL) { Staff* c = newStaffFactory->staffDetails(); c->input(); stafflist.AddNode(newStaffFactory); stafflist.PrintList(); }

However the print list function is not working

void List::AddNode(StaffFactory* c) //function to add node { List::Node* n = new List::Node; n->next = NULL; n->newstaff = c; if (head == NULL) //check if the list is empty { head = n; } else { curr = head; //start of the list and iterates till next points to end of the list while (curr->next != NULL) { curr = curr->next; } curr->next = n; } cout << "New Node added" << endl; } void List::PrintList() //print nodes in the list { curr = head; while (curr != NULL) //each node is printed till current pointer gets to end of the list { curr->newstaff->staffDetails(); curr = curr->next; } cout << "The linked list printed" << endl; }

[Salil Wadnerkar]

I think you got this code from somewhere else, and trying to make it work. There are many things wrong with this code.
Your linked list is of StaffFactory instances, instead of Staff instances you create. Your print list does not print. There are just two things that stand out.
I suggest - instead of writing so many classes (abstractions) beforehand, approach the problem step by step.
1. Create a new staff of just one type first, add it to linked list, print the linked list.
2. Once this is working, create different types of Staff in your code (not from user input), and make sure the linked list is still working.
3. Add user input, and dynamic creation of different staff instances.

[John Matthews]

Hi Debie

I'm more C than C++, but I can spot something that looks wrong. Your Staff class has Name, Address and age fields, which is fine. But then JuniorStaff is a sub-class of Staff, so it inherits Staff's Name, Address and age fields, and it shouldn't have its own Name, Address and age fields. Similarly for MgtStaff.

And JuniorStaff::display() only needs to call Staff::display() to display its inherited Name, Address and age fields, plus a line to display the JuniorStaff-specific staffLevel field. Similarly for MgtStaff::display().

I suggest reading up on C++ inheritance before going any further - something like this https://www.geeksforgeeks.org/inheritance-in-c/ although others might have better suggestions.

Cheers
John

[John Matthews]

To answer your question, I think the main problem with your linked list is that the nodes contain StaffFactory (pointers to) objects. I think they should be Staff?

I've changed StaffFactory to Staff in the StaffList.cpp/h files, changed List::PrintList() to call Staff::display(), and passed c and d to staffList.AddNode() in main(). I've also corrected the code as suggested in my previous post. And the code basically works.

Have a go at making these changes and see how it goes.

Cheers
John