Example for Blog Post "Hexagonal Architecture: Structuring a project and the influence of granularity"

driven_ports.go

# the coarse-grained version

type ForStoringEvents interface {
  CreateEventStream(streamID lib.StreamID, event lib.Event) error
  AppendEventsToStream(
    streamID lib.StreamID,
    expectedRevision uint64,
    recordedEvents ...lib.Event,
  ) error
  ReadEventStream(streamID lib.StreamID) (lib.EventStream, error)
}

# the fine-grained version

type ForCreatingEventStreams interface {
  Create(streamID lib.StreamID, event lib.Event) error
}

type ForAppendingEventsToStreams interface {
  Append(
    streamID lib.StreamID,
	  expectedRevision uint64,
	  recordedEvents ...lib.Event,
  ) error
}

type ForReadingEventStreams interface {
  Read(streamID lib.StreamID) (lib.EventStream, error)
}