In Domain-Driven Design (DDD), both Factory and Repository patterns play crucial roles, but they serve different purposes and are used in distinct contexts.
Factory Pattern
Purpose:
The Factory pattern is a creational design pattern used to encapsulate the logic for creating instances of complex domain objects, particularly Aggregate Roots or entities that require intricate construction logic. Factories ensure that objects are always created in a consistent and valid state.
Key Characteristics:
Object Creation: Factories handle the creation of complex objects, abstracting the instantiation process from the client code.
Consistency: They ensure that the created objects are always in a valid state by encapsulating the construction logic.
Complex Initialization: Factories are particularly useful when the creation process involves multiple steps or dependencies.
Types of Factories: There are different types of factories, such as Factory Methods and Abstract Factories, which can be used depending on the complexity and requirements of the object creation process.
Example:
A CustomerFactory might be responsible for creating instances of Customer entities with various attributes, roles, and permissions, ensuring that all necessary fields are initialized correctly[1][8][14].
Repository Pattern
Purpose:
The Repository pattern is a structural design pattern used to abstract data access and persistence logic from the domain model. Repositories provide a standardized interface for querying and storing domain objects, hiding the details of how data is retrieved or stored.
Key Characteristics:
Data Access Abstraction: Repositories act as an intermediary between the domain model and the data source, providing a way to store and retrieve domain objects without exposing the underlying data access details.
Separation of Concerns: They decouple the domain logic from the persistence logic, promoting a clear separation of concerns.
Collection-Like Interface: Repositories often provide a collection-like interface, allowing operations such as add, remove, and query on domain objects.
Persistence: They handle the persistence of domain objects, ensuring that changes to the objects are saved to the database or other storage mechanisms.
Example:
A CustomerRepository might provide methods for querying and storing Customer entities, such as Add(Customer customer), Remove(Customer customer), and GetById(int id)[2][4][7].
