Types of Factories in Domain Driven Design

There are three main types of factories in DDD:

1. Domain factories: These factories are responsible for creating instances of domain objects, which are the core building blocks of a DDD model. Domain factories typically encapsulate the business logic related to object creation, such as validating input data and setting default values.

   Domain factories Examples:

   1. UserFactory:

   • Responsible for creating instances of the User domain object.

   • Validates user input data, ensuring that required fields are present and meet certain criteria.

   • Sets default values for optional user attributes if not provided.

   2. OrderFactory:

   • Creates instances of the Order domain object.

   • Validates order details, such as item quantities, prices, and shipping information.

   • Enforces business rules related to order creation, such as ensuring that an order must have at least one item.

   3. ProductFactory:
      • Manages the creation of Product domain objects.
      • Validates product information like name, description, and pricing.
      • Sets default values for properties like product availability status.

2. Repository factories: These factories are responsible for creating instances of repositories, which are objects that provide access to persistent data. Repository factories can help to decouple the application from the underlying data store, and they can make it easier to switch between different data storage technologies.

   Repository factories Examples:

   1. UserRepositoryFactory:
      • Creates instances of the UserRepository responsible for handling user data storage and retrieval.
      • Abstracts the creation of the underlying data store connection or technology.
      • Enables easy switching between different database implementations.
   2. OrderRepositoryFactory:
      • Generates instances of the OrderRepository for managing order persistence.
      • Abstracts away the details of how orders are stored, allowing for flexibility in choosing a database or storage solution.
      • Configures the repository with necessary parameters, such as connection strings.
   3. ProductRepositoryFactory:
      • Creates instances of the ProductRepository for handling product data.
      • Abstracts the details of interacting with the specific data store, promoting loose coupling.
      • Configures the repository with caching or other performance-related settings.

3. Service factories: These factories are responsible for creating instances of services, which are objects that provide business functionality. Service factories can help to organize and manage the application's services, and they can make it easier to test and maintain the application.

   Service factories Examples:

   1. PaymentServiceFactory:
      • Responsible for creating instances of the PaymentService that handles payment processing.
      • Configures the service with necessary dependencies, such as external payment gateways or processors.
      • Enables easy substitution of payment service implementations for testing or integration purposes.
   2. ShippingServiceFactory:
      • Creates instances of the ShippingService for managing the shipment of orders.
      • Configures the service with shipping providers, delivery rules, and other necessary components.
      • Facilitates the substitution of different shipping service implementations.
   3. AuthenticationServiceFactory:
      • Generates instances of the AuthenticationService for handling user authentication.
      • Configures the service with security policies, token generation strategies, etc.
      • Allows for easy replacement of authentication mechanisms or policies.