🛒 Sales & Purchase App – Factory Method Pattern Demo

📌 Overview

This project is a simple sales and purchase application built in C++, showcasing the use of the Factory Method Design Pattern.

We apply the Factory Method to create:

• Various Products (e.g., Book, Electronic)
• Different Users (Customer, Seller)
• Multiple Payment Methods

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🏗️ Project Structure

src/
├── payments/
│   ├── PaymentMethod.cpp / .h
│   ├── PaymentMethodFactory.cpp / .h
│
├── products/
│   ├── Product.cpp / .h
│   ├── Book.cpp / .h
│   ├── Electronic.cpp / .h
│   ├── ProductFactory.cpp / .h
│
├── users/
│   ├── User.cpp / .h
│   ├── Customer.cpp / .h
│   ├── Seller.cpp / .h
│   ├── UserFactory.cpp / .h
│
├── ApplicationController.cpp / .h
└── main.cpp

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🧠 Design Pattern: Factory Method

Why Factory Method?

Without Factory Method:

• Classes like ApplicationController would be tightly coupled to concrete classes (Book, Seller, etc.)
• Adding new types would require modifying existing logic

With Factory Method:

• Object creation is delegated to factory classes
• Promotes extensibility and loose coupling

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💡 Example Usage

// Using Product Factory
ProductFactory* productFactory = new ProductFactory();
Product* product = productFactory->createProduct("Book");

// Using User Factory
UserFactory* userFactory = new UserFactory();
User* user = userFactory->createUser("Seller");

// Using Payment Method Factory
PaymentMethodFactory* paymentFactory = new PaymentMethodFactory();
PaymentMethod* method = paymentFactory->createPayment("CreditCard");

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✅ Benefits

• 🔧 Easy to Extend: Add new users/products/payment methods without changing existing core logic
• 🔄 Reusability: Shared behavior is reused via base classes/interfaces
• 🧩 Loose Coupling: Application code works with abstract types
• 🔐 Encapsulation: Object creation details are hidden

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🖥️ Build & Run

cd src
g++ -std=c++17 *.cpp payments/*.cpp products/*.cpp users/*.cpp -o shop_app
./shop_app

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💡 Future Improvements

• Add new product types (ClothingProduct, ServiceProduct)
• Add user roles (AdminUser)
• Integrate payment gateway (Stripe, PayPal)
• Add GUI using Qt or a web-based frontend

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👨‍💻 Contributors

This project was developed by:

• JakeConal (Hieu Nguyen)
• kyrie25 (Nam Anh)
• emanhthangngot