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Dito.js Models

Dito.js Models are an extension of Objection.js' Model class. Objection.js is a very powerful, versatile and modern ORM for Node.js. Instead of fully abstracting away the complexity of SQL behind object-oriented structures as normal ORMs often do, Objection.js is built around a mighty and elegant SQL query builder (itself based on Knex.js), deploying OOP patterns only where they make sense, but never trying to completely hide away the presence of SQL.

The result is an ORM that is more flexible and dynamic in its treatment of SQL than most, making it at once powerful yet enjoyable to work with. You will often find that Objection.js abstracts away the tricky or yucky parts of SQL while preserving its power and potential to create and process data in complex ways.

Just like in Objection.js, a Dito.js Model class represents a database table and instances of that class represent table rows. See Migrations for more information on how to create database tables to go along with the Model classes, as well as how database table and column names are mapped to Dito.js classes and properties.

Dito.js Models differ from Objection.js Models in a row of extensions aimed at making declarative model configuration more streamlined and convention based.

Model Definitions

Normally, models are created in the src/server/models folder. Models extend the Model class provided by Dito.js Server, which in turn extends the underlying Objection.js Model class:

import { Model } from '@ditojs/server'

export class MyModel extends Model {
  static properties = {
  }

  static relations = {
  }

  static scopes = {
  }

  static filters = {
  }

  static someClassMethod() {
  }

  someInstanceMethod() {
  }
}

Models describe their properties, relations, scopes, and filters as static class properties. Just like with any class in JS, they can also define methods, both as static class methods, and as instance methods. Read more on the definition of each type in these separate chapters:

Note: When inheriting from other Model classes that already provide such definitions, all the definitions from the Model classes' inheritance chain get merged into one. While with methods, normal JS class inheritance can be used and previous definitions can be accessed through the super keyword, other strategies are deployed for properties, relations, scopes and filters:

Their processed, merged state is automatically reflected by Dito.js in the static Model.definition property, which holds precomputed entries for each definition:

Model.definition = {
  properties: {},
  relations: {},
  scopes: {},
  filters: {}
}

Model Queries

Dito.js inherits Objection.js' QueryBuilder class and extends it further with useful additions that align well with the Dito.js way of doing things. Read more on queries here:

Differences to Objection.js

Each chapter linked to above contains a sub-chapter listing the differences to Objection.js, e.g. Model Properties – Differences to Objection.js Once these differences are understood, you should be able to consult the useful and detailed documentation of Objection.js without causing confusion between the two libraries.

On a level of model definitions, these are the differences to Objection.js:

  • Objection.js doesn't inherit and merge model definitions across a model classes' inheritance chain, and doesn't and keep them around in a static Model.definition field.