Two models referencing same table

Version: 2.1.2 Problem: I have a post table that is responsible for a number of objects in our app (posts, blog posts, messages, replies, notifications, etc.) I would like to create a class for each and have that class instantiated with a scope (i.e. post_type == 'notification', post_type == 'message', etc.) each with their own custom relations.

In Laravel they call it global scopes, and have been going through the Objection.js documentation to see if there is something similar. The closest I found is Modifiers.

Preferred API:

// Posts
class Post extends Model {
  static get tableName() {
    return 'posts';
  }
}

// Message
class Message extends Model {
  static get tableName() {
    return 'posts'
  }

  function globalScope(query) {
    return query.where('post_type', '=', 'message')
  }
}

// Blog
class Blog extends Model {
  static get tableName() {
    return 'posts'
  }

  function globalScope(query) {
    return query.where('post_type', '=', 'blog')
  }
}

[wwei-flux]

Curious to know if this is recognized as a pattern to handle the “multiple models sharing a table” aka. the Single Table Inheritance pattern. It’s a relatively common pattern that several concept “models” have similar underlying data structures but different business logic, so we want them to share a DB table, but separate models to separate logic.

I hope Objection.js can recognize it as a pattern/recipe and support it. The issue reported about upsertGraph in the last comment is a concern of whether we should use it or not.

[koskimas]

$parseJson should work just fine. Another option is $beforeInsert and $beforeUpdate.

Oddly enough, I was able to remove the fromDatabaseJson method from the Person class you posted above. My inserts and queries are still working fine.

That was just for turning the items into correct class when they are queries through Post. Like this

const posts = await Post.query()

posts[0] instanceof Message
posts[1] instanceof Blog
...