Integrating ROM into Hanami 2.2

[dcr8898]

@alassek

I think this is pretty explicit already simply by virtue of the DAG structure of Slices.

Relations are the object that represent your Database objects. They define what tables you access and how the data types are coerced into Ruby types, and how they relate to one another.

If multiple Slices share the same DB data, then they will either 1) share the literal Relation object via a parent Slice, or 2) define their own relationship to this data separately. I can see arguments for both.

I model all my data as use-cases. This avoids a common pitfall of Rails models where they accumulate data from all use-cases and you’re always generally exposed to this expansion in role. This happens because the Active Record pattern defines one class per DB table.

The major conceptual difference with ROM is that you should always model your data to the specific use it’s being applied. So even though it might be expedient to colocate certain data in the DB, this is entirely abstracted from the application layer. Thus the locality of this data can change without impacting business logic.

MINI RANT: Seriously, you need to blog. You have a massive amount of practical experience that I would love to learn from. Example: you mentioned your Either helper in passing in the dry-rb Discourse, and I had to Google to find more complete information in the Rails Discourse, and then just last week you dropped it into a convo here–as in, here in this Discourse. Just write a blog, man. Or a Udemy course or something. If you don’t want the hassle, I’m down to help. Seriously. Rant over.

I would love to learn more about the way you model data. I relate what you are saying about ActiveRecord to what Scott Bellware (of Eventide) calls the “monolithic database” (not a compliment). But I’m not clear on how the practices you describe help to avoid potential database coupling across slices (not just down the acyclic graph) if a single database is available to all slices without additional guardrails.