# frozen_string_literal: true module ActiveRecord # = Active Record \Callbacks # # \Callbacks are hooks into the life cycle of an Active Record object that allow you to trigger logic # before or after a change in the object state. This can be used to make sure that associated and # dependent objects are deleted when {ActiveRecord::Base#destroy}[rdoc-ref:Persistence#destroy] is called (by overwriting +before_destroy+) or # to massage attributes before they're validated (by overwriting +before_validation+). # As an example of the callbacks initiated, consider the {ActiveRecord::Base#save}[rdoc-ref:Persistence#save] call for a new record: # # * (-) save # * (-) valid # * (1) before_validation # * (-) validate # * (2) after_validation # * (3) before_save # * (4) before_create # * (-) create # * (5) after_create # * (6) after_save # * (7) after_commit # # Also, an after_rollback callback can be configured to be triggered whenever a rollback is issued. # Check out ActiveRecord::Transactions for more details about after_commit and # after_rollback. # # Additionally, an after_touch callback is triggered whenever an # object is touched. # # Lastly an after_find and after_initialize callback is triggered for each object that # is found and instantiated by a finder, with after_initialize being triggered after new objects # are instantiated as well. # # There are nineteen callbacks in total, which give a lot of control over how to react and prepare for each state in the # Active Record life cycle. The sequence for calling {ActiveRecord::Base#save}[rdoc-ref:Persistence#save] for an existing record is similar, # except that each _create callback is replaced by the corresponding _update callback. # # Examples: # class CreditCard < ActiveRecord::Base # # Strip everything but digits, so the user can specify "555 234 34" or # # "5552-3434" and both will mean "55523434" # before_validation(on: :create) do # self.number = number.gsub(/[^0-9]/, "") if attribute_present?("number") # end # end # # class Subscription < ActiveRecord::Base # before_create :record_signup # # private # def record_signup # self.signed_up_on = Date.today # end # end # # class Firm < ActiveRecord::Base # # Disables access to the system, for associated clients and people when the firm is destroyed # before_destroy { |record| Person.where(firm_id: record.id).update_all(access: 'disabled') } # before_destroy { |record| Client.where(client_of: record.id).update_all(access: 'disabled') } # end # # == Inheritable callback queues # # Besides the overwritable callback methods, it's also possible to register callbacks through the # use of the callback macros. Their main advantage is that the macros add behavior into a callback # queue that is kept intact through an inheritance hierarchy. # # class Topic < ActiveRecord::Base # before_destroy :destroy_author # end # # class Reply < Topic # before_destroy :destroy_readers # end # # When Topic#destroy is run only +destroy_author+ is called. When Reply#destroy is # run, both +destroy_author+ and +destroy_readers+ are called. # # *IMPORTANT:* In order for inheritance to work for the callback queues, you must specify the # callbacks before specifying the associations. Otherwise, you might trigger the loading of a # child before the parent has registered the callbacks and they won't be inherited. # # == Types of callbacks # # There are three types of callbacks accepted by the callback macros: method references (symbol), callback objects, # inline methods (using a proc). Method references and callback objects are the recommended approaches, # inline methods using a proc are sometimes appropriate (such as for creating mix-ins). # # The method reference callbacks work by specifying a protected or private method available in the object, like this: # # class Topic < ActiveRecord::Base # before_destroy :delete_parents # # private # def delete_parents # self.class.delete_by(parent_id: id) # end # end # # The callback objects have methods named after the callback called with the record as the only parameter, such as: # # class BankAccount < ActiveRecord::Base # before_save EncryptionWrapper.new # after_save EncryptionWrapper.new # after_initialize EncryptionWrapper.new # end # # class EncryptionWrapper # def before_save(record) # record.credit_card_number = encrypt(record.credit_card_number) # end # # def after_save(record) # record.credit_card_number = decrypt(record.credit_card_number) # end # # alias_method :after_initialize, :after_save # # private # def encrypt(value) # # Secrecy is committed # end # # def decrypt(value) # # Secrecy is unveiled # end # end # # So you specify the object you want to be messaged on a given callback. When that callback is triggered, the object has # a method by the name of the callback messaged. You can make these callbacks more flexible by passing in other # initialization data such as the name of the attribute to work with: # # class BankAccount < ActiveRecord::Base # before_save EncryptionWrapper.new("credit_card_number") # after_save EncryptionWrapper.new("credit_card_number") # after_initialize EncryptionWrapper.new("credit_card_number") # end # # class EncryptionWrapper # def initialize(attribute) # @attribute = attribute # end # # def before_save(record) # record.send("#{@attribute}=", encrypt(record.send("#{@attribute}"))) # end # # def after_save(record) # record.send("#{@attribute}=", decrypt(record.send("#{@attribute}"))) # end # # alias_method :after_initialize, :after_save # # private # def encrypt(value) # # Secrecy is committed # end # # def decrypt(value) # # Secrecy is unveiled # end # end # # == before_validation* returning statements # # If the +before_validation+ callback throws +:abort+, the process will be # aborted and {ActiveRecord::Base#save}[rdoc-ref:Persistence#save] will return +false+. # If {ActiveRecord::Base#save!}[rdoc-ref:Persistence#save!] is called it will raise an ActiveRecord::RecordInvalid exception. # Nothing will be appended to the errors object. # # == Canceling callbacks # # If a before_* callback throws +:abort+, all the later callbacks and # the associated action are cancelled. # Callbacks are generally run in the order they are defined, with the exception of callbacks defined as # methods on the model, which are called last. # # == Ordering callbacks # # Sometimes application code requires that callbacks execute in a specific order. For example, a +before_destroy+ # callback (+log_children+ in this case) should be executed before records in the +children+ association are destroyed by the # dependent: :destroy option. # # Let's look at the code below: # # class Topic < ActiveRecord::Base # has_many :children, dependent: :destroy # # before_destroy :log_children # # private # def log_children # # Child processing # end # end # # In this case, the problem is that when the +before_destroy+ callback is executed, records in the +children+ association no # longer exist because the {ActiveRecord::Base#destroy}[rdoc-ref:Persistence#destroy] callback was executed first. # You can use the +prepend+ option on the +before_destroy+ callback to avoid this. # # class Topic < ActiveRecord::Base # has_many :children, dependent: :destroy # # before_destroy :log_children, prepend: true # # private # def log_children # # Child processing # end # end # # This way, the +before_destroy+ is executed before the dependent: :destroy is called, and the data is still available. # # Also, there are cases when you want several callbacks of the same type to # be executed in order. # # For example: # # class Topic < ActiveRecord::Base # has_many :children # # after_save :log_children # after_save :do_something_else # # private # def log_children # # Child processing # end # # def do_something_else # # Something else # end # end # # In this case the +log_children+ is executed before +do_something_else+. # The same applies to all non-transactional callbacks. # # As seen below, in case there are multiple transactional callbacks the order # is reversed. # # For example: # # class Topic < ActiveRecord::Base # has_many :children # # after_commit :log_children # after_commit :do_something_else # # private # def log_children # # Child processing # end # # def do_something_else # # Something else # end # end # # In this case the +do_something_else+ is executed before +log_children+. # # == \Transactions # # The entire callback chain of a {#save}[rdoc-ref:Persistence#save], {#save!}[rdoc-ref:Persistence#save!], # or {#destroy}[rdoc-ref:Persistence#destroy] call runs within a transaction. That includes after_* hooks. # If everything goes fine a +COMMIT+ is executed once the chain has been completed. # # If a before_* callback cancels the action a +ROLLBACK+ is issued. You # can also trigger a +ROLLBACK+ raising an exception in any of the callbacks, # including after_* hooks. Note, however, that in that case the client # needs to be aware of it because an ordinary {#save}[rdoc-ref:Persistence#save] will raise such exception # instead of quietly returning +false+. # # == Debugging callbacks # # The callback chain is accessible via the _*_callbacks method on an object. Active Model \Callbacks support # :before, :after and :around as values for the kind property. The kind property # defines what part of the chain the callback runs in. # # To find all callbacks in the +before_save+ callback chain: # # Topic._save_callbacks.select { |cb| cb.kind.eql?(:before) } # # Returns an array of callback objects that form the +before_save+ chain. # # To further check if the before_save chain contains a proc defined as rest_when_dead use the filter property of the callback object: # # Topic._save_callbacks.select { |cb| cb.kind.eql?(:before) }.collect(&:filter).include?(:rest_when_dead) # # Returns true or false depending on whether the proc is contained in the +before_save+ callback chain on a Topic model. # module Callbacks extend ActiveSupport::Concern CALLBACKS = [ :after_initialize, :after_find, :after_touch, :before_validation, :after_validation, :before_save, :around_save, :after_save, :before_create, :around_create, :after_create, :before_update, :around_update, :after_update, :before_destroy, :around_destroy, :after_destroy, :after_commit, :after_rollback ] module ClassMethods include ActiveModel::Callbacks ## # :method: after_initialize # # :call-seq: after_initialize(*args, &block) # # Registers a callback to be called after a record is instantiated. See # ActiveRecord::Callbacks for more information. ## # :method: after_find # # :call-seq: after_find(*args, &block) # # Registers a callback to be called after a record is instantiated # via a finder. See ActiveRecord::Callbacks for more information. ## # :method: after_touch # # :call-seq: after_touch(*args, &block) # # Registers a callback to be called after a record is touched. See # ActiveRecord::Callbacks for more information. ## # :method: before_save # # :call-seq: before_save(*args, &block) # # Registers a callback to be called before a record is saved. See # ActiveRecord::Callbacks for more information. ## # :method: around_save # # :call-seq: around_save(*args, &block) # # Registers a callback to be called around the save of a record. See # ActiveRecord::Callbacks for more information. ## # :method: after_save # # :call-seq: after_save(*args, &block) # # Registers a callback to be called after a record is saved. See # ActiveRecord::Callbacks for more information. ## # :method: before_create # # :call-seq: before_create(*args, &block) # # Registers a callback to be called before a record is created. See # ActiveRecord::Callbacks for more information. ## # :method: around_create # # :call-seq: around_create(*args, &block) # # Registers a callback to be called around the creation of a record. See # ActiveRecord::Callbacks for more information. ## # :method: after_create # # :call-seq: after_create(*args, &block) # # Registers a callback to be called after a record is created. See # ActiveRecord::Callbacks for more information. ## # :method: before_update # # :call-seq: before_update(*args, &block) # # Registers a callback to be called before a record is updated. See # ActiveRecord::Callbacks for more information. ## # :method: around_update # # :call-seq: around_update(*args, &block) # # Registers a callback to be called around the update of a record. See # ActiveRecord::Callbacks for more information. ## # :method: after_update # # :call-seq: after_update(*args, &block) # # Registers a callback to be called after a record is updated. See # ActiveRecord::Callbacks for more information. ## # :method: before_destroy # # :call-seq: before_destroy(*args, &block) # # Registers a callback to be called before a record is destroyed. See # ActiveRecord::Callbacks for more information. ## # :method: around_destroy # # :call-seq: around_destroy(*args, &block) # # Registers a callback to be called around the destruction of a record. # See ActiveRecord::Callbacks for more information. ## # :method: after_destroy # # :call-seq: after_destroy(*args, &block) # # Registers a callback to be called after a record is destroyed. See # ActiveRecord::Callbacks for more information. end included do include ActiveModel::Validations::Callbacks define_model_callbacks :initialize, :find, :touch, only: :after define_model_callbacks :save, :create, :update, :destroy end def destroy # :nodoc: @_destroy_callback_already_called ||= false return if @_destroy_callback_already_called @_destroy_callback_already_called = true _run_destroy_callbacks { super } rescue RecordNotDestroyed => e @_association_destroy_exception = e false ensure @_destroy_callback_already_called = false end def touch(*, **) # :nodoc: _run_touch_callbacks { super } end def increment!(attribute, by = 1, touch: nil) # :nodoc: touch ? _run_touch_callbacks { super } : super end private def create_or_update(**) _run_save_callbacks { super } end def _create_record _run_create_callbacks { super } end def _update_record _run_update_callbacks { super } end end end