Onion Architecture

Onion Architecture is a software architectural patterns that emphasizes the separation of concerns and dependency inversion.

Layers of Onion Architecture

1. Core (Domain) Layer: Contains the business logic and domain entities. This layer is independent of any other layers and does not depend on external libraries or frameworks.
2. Application Layer: Contains application-specific logic, such as use cases and services. This layer coordinates the flow of data between the domain and outer layers.
3. Infrastructure Layer: Contains implementations for external concerns, such as data access, messaging, and other services. This layer depends on the application and domain layers.
4. Presentation Layer: Contains the user interface and API controllers. This layer depends on teh application layer and interacts with the user or external systems.

Concepts related to each Layer

1. Core (Domain) Layer
   • Domain-Driven Design (DDD)
   • What is the relationship between DDD and "Onion Architecture"?

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   • Interfaces
   • Entities: Objects with a unique identity, state and behavior
   • Value Objects
   • Aggregates
2. Application Layer
   • Services
3. Infrastructure Layer
   • Repositories
   • Data Source
4. Presentation Layer
   • Controller

• https://jeffreypalermo.com/2008/07/the-onion-architecture-part-1/