DOCSP-45361: callbacks

snooty.toml

@@ -31,3 +31,4 @@ server-manual = "Server manual"
 api-root = "https://www.mongodb.com/docs/mongoid/master/api/Mongoid"
 api = "https://www.mongodb.com/docs/mongoid/master/api"
 ruby-api = "https://www.mongodb.com/docs/ruby-driver/current/api/Mongo"
+active-record-docs = "https://guides.rubyonrails.org"

source/add-existing.txt

@@ -130,10 +130,10 @@ for each Rails component, as shown in the following sample
 .. note::
 
    Because they rely on Active Record, the `ActionText
-   <https://guides.rubyonrails.org/action_text_overview.html>`__,
+   <{+active-record-docs+}/action_text_overview.html>`__,
    `ActiveStorage <https://edgeguides.rubyonrails.org/active_storage_overview.html>`__, and
    `ActionMailbox
-   <https://guides.rubyonrails.org/action_mailbox_basics.html>`__
+   <{+active-record-docs+}/action_mailbox_basics.html>`__
    adapters cannot be used alongside {+odm+}.
 
 Disable Active Record Adapters

source/data-modeling.txt

@@ -20,6 +20,7 @@ Model Your Data
    Persistence Configuration </data-modeling/persistence-configuration>
    Inheritance </data-modeling/inheritance>
    Document Validation </data-modeling/validation>
+   Callbacks </data-modeling/callbacks>
    Data Associations </data-modeling/associations>
    Optimize Queries With Indexes </data-modeling/indexes>
 
@@ -43,6 +44,9 @@ In this section, you can learn how to model data in {+odm+}.
 - :ref:`mongoid-modeling-validation`: Learn how to create document
   validation rules for your model classes.
 
+- :ref:`mongoid-modeling-callbacks`: Learn how to implement callbacks to
+  customize the life cycle of your models.
+
 - :ref:`mongoid-associations`: Learn how to create and manage data
   associations in your model classes.
 

source/data-modeling/callbacks.txt

@@ -0,0 +1,178 @@
+.. _mongoid-modeling-callbacks:
+
+=========
+Callbacks
+=========
+
+.. facet::
+   :name: genre
+   :values: reference
+
+.. meta::
+   :keywords: ruby framework, odm, code example, life cycle
+
+.. contents:: On this page
+   :local:
+   :backlinks: none
+   :depth: 2
+   :class: singlecol
+
+Overview
+--------
+
+In this guide, you can learn how to implement **callbacks** in your
+{+odm+} models to customize the life cycle of your model instances.
+
+Callbacks are methods that {+odm+} triggers at specified moments of
+an object's life cycle. They allow you to initiate specified actions
+before or after changes to an object's state.
+
+{+odm+} implements many of the callbacks from Active Record. To learn
+more, see `Callbacks
+<{+active-record-docs+}/active_record_callbacks.html>`__ in the
+Active Record documentation.
+
+Supported Callbacks
+-------------------
+
+Mongoid supports the following callbacks on model classes that implement
+the :ref:`Document <mongoid-modeling-documents>` module:
+
+-  ``after_initialize``
+-  ``after_build``
+-  ``before_validation``
+-  ``after_validation``
+-  ``before_create``
+-  ``around_create``
+-  ``after_create``
+-  ``after_find``
+-  ``before_update``
+-  ``around_update``
+-  ``after_update``
+-  ``before_upsert``
+-  ``around_upsert``
+-  ``after_upsert``
+-  ``before_save``
+-  ``around_save``
+-  ``after_save``
+-  ``before_destroy``
+-  ``around_destroy``
+-  ``after_destroy``
+
+To learn more about any of the preceding callback types, see the
+`ActiveRecord::Callbacks
+<https://api.rubyonrails.org/{+rails-8-version-docs+}/classes/ActiveRecord/Callbacks.html>`__
+reference in the Rails API documentation.
+
+You can implement callbacks in both top-level and embedded document
+models.
+
+.. note:: Callback Invocation Behavior
+
+   For efficiency, {+odm+} invokes the callback only on the document
+   that you performed the persistence action on. This behavior enables
+   {+odm+} to support large hierarchies and handle optimized atomic
+   updates efficiently by not invoking callbacks throughout the document
+   hierarchy.
+
+Take precautions and ensure testability when implementing callbacks for
+domain logic, because these designs can lead to unexpected errors when
+callbacks in the chain halt execution. We recommend using callbacks for
+cross-cutting concerns outside of your program's core functionality,
+such as queueing up background jobs.
+
+Document Callbacks
+------------------
+
+You must implement and register callbacks on your model classes.
+You can register a callback by using ordinary methods, blocks and
+``Proc`` objects, or by defining custom callback objects that use
+classes or modules.
+
+This example demonstrates how to register callbacks on the ``Contact``
+model class in the following ways:
+
+- Includes the ``before_save`` class method, which triggers the
+  ``process_phone`` method before a ``Contact`` instance is saved to
+  MongoDB. The ``process_phone`` method is defined separately in the class.
+
+- Includes the ``after_destroy`` class method and uses a block to print a
+  message when a ``Contact`` instance is deleted.
+
+.. literalinclude:: /includes/data-modeling/callbacks.rb
+   :start-after: start-doc-callback
+   :end-before: end-doc-callback
+   :language: ruby
+   :emphasize-lines: 8, 11-13, 16-18
+   :dedent:
+
+The following code performs data operations that demonstrate the
+callback actions:
+
+.. literalinclude:: /includes/data-modeling/callbacks.rb
+   :start-after: start-doc-ops
+   :end-before: end-doc-ops
+   :language: ruby
+   :dedent:
+
+Because callback functionality comes from Active Support, you can
+alternatively use the ``set_callback`` class method syntax to register
+callbacks. The following code demonstrates how to use this syntax to
+create a callback that stores original values of the ``name`` field in
+the ``aliases`` array:
+
+.. literalinclude:: /includes/data-modeling/callbacks.rb
+   :start-after: start-doc-set-syntax
+   :end-before: end-doc-set-syntax
+   :language: ruby
+   :emphasize-lines: 8-12
+   :dedent:
+
+Association Callbacks
+---------------------
+
+{+odm+} provides the following association callbacks:
+
+- ``after_add``
+- ``after_remove``
+- ``before_add``
+- ``before_remove``
+
+If you register an association callback on your model class, it is
+invoked whenever you add or remove a document from any of the following
+associations:
+
+- ``embeds_many``
+- ``has_many``
+- ``has_and_belongs_to_many``
+
+Specify association callbacks as options on the respective association.
+You must pass the added or removed document as the parameter to the
+specified callback.
+
+The following code demonstrates how to register an association callback
+on a ``User`` model class that embeds multiple ``SavedArticle``
+instances to limit the number of embedded documents for a single
+instance:
+
+.. literalinclude:: /includes/data-modeling/callbacks.rb
+   :start-after: start-association-callback
+   :end-before: end-association-callback
+   :language: ruby
+   :emphasize-lines: 6, 10-15
+   :dedent:
+
+Additional Information
+----------------------
+
+To learn how to prevent {+odm+} from running callbacks, see the
+following references in the Active Record documentation:
+
+- `Skipping Callbacks <{+active-record-docs+}/active_record_callbacks.html#skipping-callbacks>`__
+- `Suppressing Saving <{+active-record-docs+}/active_record_callbacks.html#suppressing-saving>`__
+
+To learn about how {+odm+} manages callbacks in transactions, see the
+:ref:`mongoid-data-txn` guide.
+
+To learn how to access and change your MongoDB data, see the
+:ref:`mongoid-interact-data` guides.

source/data-modeling/validation.txt

@@ -29,7 +29,7 @@ of document fields in your collections.
 {+odm+} includes ``ActiveModel::Validations`` from Active Record to
 provide validation functionality, including an associated and uniqueness
 validator. To learn more, see the `Active Record Validations
-<https://guides.rubyonrails.org/active_record_validations.html>`__
+<{+active-record-docs+}/active_record_validations.html>`__
 Rails guide and `ActiveModel::Validations
 <https://api.rubyonrails.org/classes/ActiveModel/Validations.html>`__
 Rails API documentation.
@@ -284,14 +284,14 @@ Custom Validation Rules
 You can use the ``validates_each`` and ``validates_with`` helpers to
 create custom validators. To learn more about these helpers and view
 examples, see the `validates_each
-<https://guides.rubyonrails.org/active_record_validations.html#validates-each>`__
+<{+active-record-docs+}/active_record_validations.html#validates-each>`__
 and `validates_with
-<https://guides.rubyonrails.org/active_record_validations.html#validates-with>`__
+<{+active-record-docs+}/active_record_validations.html#validates-with>`__
 references in the Active Record documentation.
 
 To learn more about custom validators, see `Performing Custom
 Validations
-<https://guides.rubyonrails.org/active_record_validations.html#performing-custom-validations>`__
+<{+active-record-docs+}/active_record_validations.html#performing-custom-validations>`__
 in the Active Record documentation.
 
 Behavior

source/includes/data-modeling/callbacks.rb

@@ -0,0 +1,78 @@
+# start-doc-callback
+class Contact
+  include Mongoid::Document
+
+  field :name, type: String
+  field :phone, type: String
+
+  # Creates a callback to clean phone numbers before saving
+  before_save :process_phone
+
+  protected
+    def process_phone
+      self.phone = phone.gsub(/[^0-9]/, "") if attribute_present?("phone")
+    end
+
+  # Creates a callback to send a message about object deletion
+  after_destroy do
+      p "deleted the contact for #{name}"
+  end
+end
+# end-doc-callback
+
+# start-doc-ops
+Contact.create(name: 'Serena Atherton', phone: '999 555-3030')
+# => `phone` field saved as '9995553030'
+Contact.create(name: 'Zayba Haq', phone: '999  123?5050')
+# => `phone` field saved as '9991235050'
+
+Contact.first.destroy
+# => Console message: "deleted the contact for Serena Atherton"
+# end-doc-ops
+
+# start-doc-set-syntax
+class Contact
+  include Mongoid::Document
+
+  field :name, type: String
+  field :phone, type: String
+  field :aliases, type: Array, default: []
+
+  set_callback(:update, :before) do |document|
+    if document.name_changed?
+      document.push(aliases: document.name_was)
+    end
+  end
+end
+
+Contact.create(name: 'Xavier Bloom', phone: '4447779999')
+Contact.first.update(name: 'Xav - coworker')
+# Saved document in MongoDB:
+# {"aliases":["Xavier Bloom"],"name":"Xav - coworker","phone":"4447779999"}
+# end-doc-set-syntax
+
+# start-association-callback
+class User
+  include Mongoid::Document
+
+  field :username, type: String
+  # Registers the callback in the association statement
+  embeds_many :saved_articles, before_add: :send_message
+
+  protected
+    # Passes the association document as a parameter to the callback
+    def send_message(saved_article)
+      if saved_articles.count >= 10
+        p "you can't save more than 10 articles at a time"
+        throw(:abort)
+      end
+    end
+end
+
+class SavedArticle
+  include Mongoid::Document
+  embedded_in :user
+
+  field :url, type: String
+end
+# end-association-callback

source/quick-start-rails.txt

@@ -45,7 +45,7 @@ modeled and displayed. {+odm+} replaces the default Active Record
 adapter for data modeling in Rails.
 
 To learn more about Ruby on Rails, see the `Getting Started
-with Rails <https://guides.rubyonrails.org/getting_started.html>`__
+with Rails <{+active-record-docs+}/getting_started.html>`__
 guide in the Rails documentation.
 
 MongoDB Atlas is a fully managed cloud database service that hosts your