Hooks

Hooks are the actions that you can perform against a model instance during a pre-defined life cycle event. Using hooks, you can encapsulate specific actions within your models vs. writing them everywhere inside your codebase.

A great example of hooks is password hashing. You can define a hook that runs before the save call and converts the plain text password to a hash.

app/Models/User.ts

import Hash from '@ioc:Adonis/Core/Hash'
import { column, beforeSave, BaseModel } from '@ioc:Adonis/Lucid/Orm'

export default class User extends BaseModel {
  @column({ isPrimary: true })
  public id: number

  @column()
  public email: string

  @column()
  public password: string

  @beforeSave()
  public static async hashPassword (user: User) {
    if (user.$dirty.password) {
      user.password = await Hash.make(user.password)
    }
  }
}

The beforeSave hook is invoked before the INSERT and the UPDATE queries.
Hooks can be async. So you can use the await keyword inside them.
Hooks are always defined as static functions and receive the model's instance as the first argument.

Understanding the `$dirty` property

The beforeSave hook is called every time a new user is created or updated using the model instance.

During the update, you may have updated other properties but NOT the user password. Hence there is no need to re-hash the existing hash, which is why using the $dirty object.

The $dirty object only contains the changed values. So, you can check if the password was changed and then hash the new value.

Available hooks

Following is the list of all the available hooks. Make sure to read the decorators API docs as well.

Hook	Description
`beforeSave`	Invoked before the insert or the update query. Receives the model instance as the only argument.
`afterSave`	Invoked after the insert or the update query. Receives the model instance as the only argument.
`beforeCreate`	Invoked only before the insert query. Receives the model instance as the only argument.
`afterCreate`	Invoked only after the insert query. Receives the model instance as the only argument.
`beforeUpdate`	Invoked only before the update query. Receives the model instance as the only argument.
`afterUpdate`	Invoked only after the update query. Receives the model instance as the only argument.
`beforeDelete`	Invoked before the delete query. Receives the model instance as the only argument.
`afterDelete`	Invoked after the delete query. Receives the model instance as the only argument.
`beforePaginate`	Invoked before the paginate query. Receives the query main builder instance alongside the count query builder instance.
`afterPaginate`	Invoked after the paginate query. Receives an instance of the simple paginator class.
`beforeFetch`	Invoked before the fetch query. Receives the query builder instance as the only argument.
`afterFetch`	Invoked after the fetch query. Receives an array of model instances
`beforeFind`	Invoked before the find query. Receives the query builder instance as the only argument.
`afterFind`	Invoked after the find query. Receives the model instance as the only argument.

All hooks receive the model instance as the first argument, except the ones documented below.

beforeFind

The beforeFind hook is invoked just before the query is executed to find a single row. This hook receives the query builder instance, and you can attach your constraints to it.

import {
  BaseModel,
  beforeFind,
  ModelQueryBuilderContract,
} from '@ioc:Adonis/Lucid/Orm'

export default class User extends BaseModel {
  @beforeFind()
  public static ignoreDeleted (query: ModelQueryBuilderContract<typeof User>) {
    query.whereNull('is_deleted')
  }
}

afterFind

The afterFind event receives the model instance.

import {
  BaseModel,
  afterFind,
} from '@ioc:Adonis/Lucid/Orm'

export default class User extends BaseModel {
  @afterFind()
  public static afterFindHook (user: User) {
  }
}

beforeFetch

Similar to beforeFind, the beforeFetch hook also receives the query builder instance. However, this hook is invoked whenever a query is executed without using the first method.

import {
  BaseModel,
  beforeFetch,
  ModelQueryBuilderContract,
} from '@ioc:Adonis/Lucid/Orm'

export default class User extends BaseModel {
  @beforeFetch()
  public static ignoreDeleted (query: ModelQueryBuilderContract<typeof User>) {
    query.whereNull('is_deleted')
  }
}

afterFetch

The afterFetch hook receives an array of model instances.

import {
  BaseModel,
  afterFetch,
} from '@ioc:Adonis/Lucid/Orm'

export default class User extends BaseModel {
  @afterFetch()
  public static afterFetchHook (users: User[]) {
  }
}

beforePaginate

The beforePaginate query is executed when you make use of the paginate method. The paginate method fires both the beforeFetch and beforePaginate hooks.

The hook function receives an array of query builders. The first instance is for the count's query, and the second is for the main query.

import {
  BaseModel,
  beforePaginate,
  ModelQueryBuilderContract,
} from '@ioc:Adonis/Lucid/Orm'

export default class User extends BaseModel {
  @beforePaginate()
  public static ignoreDeleted (
    countQuery: ModelQueryBuilderContract<typeof User>,
    query: ModelQueryBuilderContract<typeof User>
  ) {
    query.whereNull('is_deleted')
    countQuery.whereNull('is_deleted')
  }
}

afterPaginate

The afterPaginate hook receives an instance of the SimplePaginator class. The paginate method fires both the afterFetch and the afterPaginate hooks.

import {
  BaseModel,
  afterPaginate,
} from '@ioc:Adonis/Lucid/Orm'

import {
  SimplePaginatorContract
} from '@ioc:Adonis/Lucid/Database'

export default class User extends BaseModel {
  @afterPaginate()
  public static afterPaginateHook (users: SimplePaginatorContract<User>) {
  }
}

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