objection

Model Definition

Defines a model class that maps to a database table. In this example, the `Person` class represents the `persons` table in the database.

const { Model } = require('objection');

class Person extends Model {
  static get tableName() {
    return 'persons';
  }
}

Querying

Performs a query to fetch all persons older than 30 years. Objection.js provides a fluent API for building SQL queries.

const people = await Person.query().where('age', '>', 30);

Relations

Defines relationships between models. In this example, a `Person` can have many `Animal` pets, establishing a one-to-many relationship.

class Person extends Model {
  static get tableName() {
    return 'persons';
  }

  static get relationMappings() {
    const Animal = require('./Animal');
    return {
      pets: {
        relation: Model.HasManyRelation,
        modelClass: Animal,
        join: {
          from: 'persons.id',
          to: 'animals.ownerId'
        }
      }
    };
  }
}

Eager Loading

Fetches related data in a single query. This example fetches persons along with their pets using eager loading.

const peopleWithPets = await Person.query().withGraphFetched('pets');

Validation

Defines a JSON schema for model validation. This example ensures that `firstName` and `lastName` are required fields and must be strings of a certain length.

class Person extends Model {
  static get jsonSchema() {
    return {
      type: 'object',
      required: ['firstName', 'lastName'],
      properties: {
        id: { type: 'integer' },
        firstName: { type: 'string', minLength: 1, maxLength: 255 },
        lastName: { type: 'string', minLength: 1, maxLength: 255 }
      }
    };
  }
}