/nestjs-architecture

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NestJS Architecture & Advanced Patterns

1. Hexagonal Architecture (Ports and Adapters)

Folder structure per bounded context:

  • Application:
    • Contain the application services, modules, facades, handlers and commands.
    • This folder represents the application layer.
    • It will communicate with the data access components, message brokers and other external systems through interfaces or ports.
  • Domain:
    • Contain the domain models, value objects, domain events, factories and other domain specific components.
    • This folder represents the domain layer.
  • Infrastructure:
    • Contain the data access components, message brokers and other external systems.
    • This folder represents the infrastructure layer.
    • It will implement the interfaces (AKA. the ports) defined by the application layer.
  • Presenters or interfaces:
    • Contain the controllers, gateways and other user facing components for APIs.
    • This folder is also known/named as user interface or just interface.

More details about this structure:

  1. Value objects is an immutable object and side effect free that represent a descriptive aspect of the domain with no conceptual identity.
  2. Services must not reference DTO's (because are part of other layer). So, we should consider using payloads or commands (best option) to handle the different operations.
  3. On the controller now instead of passing the DTO we instantiate the command passing the required properties (to instantiate) using the values from the DTO.
  4. Remember that the factory is a provider (@Injectable()), so it must be registered on the module as a provider.
  5. The ports/interfaces define the contract for the interactions with the external world. While adapters implement these contracts in services in between the application layer and external systems.
/application
    /commands
    /ports
      *.repository.ts
    *.module.ts
    *.service/ts

/domain
    /factories
        *.factory.ts
    /value-objects
    *.ts (models NOT entities)

/infrastructure
  *-infrastructure.module.ts
  /persistence
    /in-memory
      ... (this is the same structure as orm but handling in memory)
    /orm
      /entities
        *.entity.ts
      /mappers
        *.mapper.ts
      /repositories
        *.repository.ts
      orm-persistence.module.ts

/presenters
    /http
        /dto
            create-*.dto.ts
            update-*.dto.ts
        *.controller.ts