Can we use a pointer for Repository assignment?

[frederikhors]

Given the repository in repository.go:

type Repository interface {
  AddTraining(ctx context.Context, tr *Training) error
  //...
}

we are creating new structs which implement that interface using code such as in trainings_firestore_repository.go:

type TrainingsFirestoreRepository struct {
  firestoreClient *firestore.Client
}

func NewTrainingsFirestoreRepository(
  firestoreClient *firestore.Client,
) TrainingsFirestoreRepository {
  return TrainingsFirestoreRepository{
    firestoreClient: firestoreClient,
  }
}

and we are create commands and queries with those structs, such as in service.go:

func newApplication(ctx context.Context, trainerGrpc command.TrainerService, usersGrpc command.UserService) app.Application {
  client, err := firestore.NewClient(ctx, os.Getenv("GCP_PROJECT"))
  //...
  trainingsRepository := adapters.NewTrainingsFirestoreRepository(client)
  //...
  return app.Application{
    Commands: app.Commands{
      ApproveTrainingReschedule: command.NewApproveTrainingRescheduleHandler(trainingsRepository, usersGrpc, trainerGrpc, logger, metricsClient),
      //...
    },
    Queries: app.Queries{
      AllTrainings:     query.NewAllTrainingsHandler(trainingsRepository, logger, metricsClient),
      //...
    },
  }
}

satisfying func signature like:

func NewApproveTrainingRescheduleHandler(
  repo training.Repository,
  //...
) decorator.CommandHandler[ApproveTrainingReschedule] {}

Question

In each func like command.NewApproveTrainingRescheduleHandler(trainingsRepository, /*...*/) we are passing trainingsRepository each time different (passed-by-value).

Can we use a pointer there avoiding maybe useless memory consumption?

[m110]

Hey @frederikhors.

Sure, there's no issue with using pointers to repositories or other adapters. In most cases, you would find the effect on memory negligible, though. In the example above, the only field of the struct is a pointer, so copying it won't be noticeable in any way.

[frederikhors]

Ok. But I'm not able to use pointers. The compiler reject it. Can you try?

[m110]

What error did you get? You will probably need to change some occurrences in the code to match pointers, but it should be straightforward.