update model relation

app/Controllers/events.ts

 import type { HttpContextContract } from '@ioc:Adonis/Core/HttpContext'
 import Event from 'App/Models/Event'
-import { Tree } from 'App/Utils/types'
 
 /**  Get all events */
 export const getAllRoots = async ({ response }: HttpContextContract) => {
@@ -10,19 +9,10 @@ export const getAllRoots = async ({ response }: HttpContextContract) => {
 }
 
 /** Recursively gives a list of sons events  */
-const getSons = async (id: number): Promise<Tree<Event>> => {
-  const event = await Event.find(id)
+const getSons = async (id: number) => {
+  const event = await Event.findOrFail(id) // Use this to throw an error automatically when the item is not found
 
-  if (!event) {
-    throw new Error('Event not found')
-  }
-
-  let sons: Tree<Event>[] = []
-  for (const sonId of event.sonIds) {
-    sons.push(await getSons(sonId))
-  }
-
-  return { father: event, sons }
+  return event.related('children').query() // Query level 1 children like this (this is not recursive)
 }
 
 /** Get all sons of a given event, using params */
@@ -64,9 +54,7 @@ export const createEvent = async ({ request, response }: HttpContextContract) =>
     return response.badRequest({ error: 'Father not found' })
   }
 
-  const event = await Event.create({ ...data, isRoot: false })
-
-  father.sonIds.push(event.id)
+  await Event.create({ ...data, isRoot: false, parentId: father.id })
   await father.save()
 
   return response.created({ message: 'Son event created' })

app/Models/Event.ts

-import { BaseModel, column } from '@ioc:Adonis/Lucid/Orm'
+import { BaseModel, HasMany, column, hasMany } from '@ioc:Adonis/Lucid/Orm'
 import { DateTime } from 'luxon'
 
 export default class Event extends BaseModel {
@@ -12,7 +12,13 @@ export default class Event extends BaseModel {
   public thumbnailId: number
 
   @column()
-  public sonIds: number[] // Represents the ids of the sons of the event (tree structure)
+  public parentId: number | null
+
+  @hasMany(() => Event, {
+    foreignKey: 'parentId', // An Event is a child of this one if its parentId is equal to this Event's id
+    localKey: 'id',
+  })
+  public children: HasMany<typeof Event>
 
   @column()
   public isRoot: boolean // Represents if the event is the root of the tree

database/migrations/1698921052424_events.ts

@@ -9,7 +9,8 @@ export default class extends BaseSchema {
       table.string('name', 255).notNullable()
       table.bigint('thumbnail_id').notNullable()
 
-      table.specificType('son_ids', 'integer[]').notNullable().defaultTo('{}')
+      // NOTE : on delete cascade will delete child events when the parent id they point to becomes invalid
+      table.integer('parent_id').nullable().references('id').inTable('events').onDelete('CASCADE')
       table.boolean('is_root').notNullable()
 
       /**