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module ActiveRecord
# = Active Record Autosave Association
#
# +AutosaveAssociation+ is a module that takes care of automatically saving
# associated records when their parent is saved. In addition to saving, it
# also destroys any associated records that were marked for destruction.
# (See +mark_for_destruction+ and <tt>marked_for_destruction?</tt>).
#
# Saving of the parent, its associations, and the destruction of marked
# associations, all happen inside a transaction. This should never leave the
# database in an inconsistent state.
#
# If validations for any of the associations fail, their error messages will
# be applied to the parent.
#
# Note that it also means that associations marked for destruction won't
# be destroyed directly. They will however still be marked for destruction.
#
# Note that <tt>:autosave => false</tt> is not same as not declaring <tt>:autosave</tt>.
# When the <tt>:autosave</tt> option is not present new associations are saved.
#
# == Validation
#
# Children records are validated unless <tt>:validate</tt> is +false+.
#
# == Callbacks
#
# Association with autosave option defines several callbacks on your
# model (before_save, after_create, after_update). Please note that
# callbacks are executed in the order they were defined in
# model. You should avoid modifying the association content, before
# autosave callbacks are executed. Placing your callbacks after
# associations is usually a good practice.
#
# == Examples
#
# === One-to-one Example
#
# class Post
# has_one :author, :autosave => true
# end
#
# Saving changes to the parent and its associated model can now be performed
# automatically _and_ atomically:
#
# post = Post.find(1)
# post.title # => "The current global position of migrating ducks"
# post.author.name # => "alloy"
#
# post.title = "On the migration of ducks"
# post.author.name = "Eloy Duran"
#
# post.save
# post.reload
# post.title # => "On the migration of ducks"
# post.author.name # => "Eloy Duran"
#
# Destroying an associated model, as part of the parent's save action, is as
# simple as marking it for destruction:
#
# post.author.mark_for_destruction
# post.author.marked_for_destruction? # => true
#
# Note that the model is _not_ yet removed from the database:
#
# id = post.author.id
# Author.find_by_id(id).nil? # => false
#
# post.save
# post.reload.author # => nil
#
# Now it _is_ removed from the database:
#
# Author.find_by_id(id).nil? # => true
#
# === One-to-many Example
#
# When <tt>:autosave</tt> is not declared new children are saved when their parent is saved:
#
# class Post
# has_many :comments # :autosave option is not declared
# end
#
# post = Post.new(:title => 'ruby rocks')
# post.comments.build(:body => 'hello world')
# post.save # => saves both post and comment
#
# post = Post.create(:title => 'ruby rocks')
# post.comments.build(:body => 'hello world')
# post.save # => saves both post and comment
#
# post = Post.create(:title => 'ruby rocks')
# post.comments.create(:body => 'hello world')
# post.save # => saves both post and comment
#
# When <tt>:autosave</tt> is true all children are saved, no matter whether they
# are new records or not:
#
# class Post
# has_many :comments, :autosave => true
# end
#
# post = Post.create(:title => 'ruby rocks')
# post.comments.create(:body => 'hello world')
# post.comments[0].body = 'hi everyone'
# post.save # => saves both post and comment, with 'hi everyone' as body
#
# Destroying one of the associated models as part of the parent's save action
# is as simple as marking it for destruction:
#
# post.comments.last.mark_for_destruction
# post.comments.last.marked_for_destruction? # => true
# post.comments.length # => 2
#
# Note that the model is _not_ yet removed from the database:
#
# id = post.comments.last.id
# Comment.find_by_id(id).nil? # => false
#
# post.save
# post.reload.comments.length # => 1
#
# Now it _is_ removed from the database:
#
# Comment.find_by_id(id).nil? # => true
module AutosaveAssociation
extend ActiveSupport::Concern
ASSOCIATION_TYPES = %w{ HasOne HasMany BelongsTo HasAndBelongsToMany }
module AssociationBuilderExtension #:nodoc:
def self.included(base)
base.valid_options << :autosave
end
def build
reflection = super
model.send(:add_autosave_association_callbacks, reflection)
reflection
end
end
included do
ASSOCIATION_TYPES.each do |type|
Associations::Builder.const_get(type).send(:include, AssociationBuilderExtension)
end
end
module ClassMethods
private
def define_non_cyclic_method(name, reflection, &block)
define_method(name) do |*args|
result = true; @_already_called ||= {}
# Loop prevention for validation of associations
unless @_already_called[[name, reflection.name]]
begin
@_already_called[[name, reflection.name]]=true
result = instance_eval(&block)
ensure
@_already_called[[name, reflection.name]]=false
end
end
result
end
end
# Adds validation and save callbacks for the association as specified by
# the +reflection+.
#
# For performance reasons, we don't check whether to validate at runtime.
# However the validation and callback methods are lazy and those methods
# get created when they are invoked for the very first time. However,
# this can change, for instance, when using nested attributes, which is
# called _after_ the association has been defined. Since we don't want
# the callbacks to get defined multiple times, there are guards that
# check if the save or validation methods have already been defined
# before actually defining them.
def add_autosave_association_callbacks(reflection)
save_method = :"autosave_associated_records_for_#{reflection.name}"
validation_method = :"validate_associated_records_for_#{reflection.name}"
collection = reflection.collection?
unless method_defined?(save_method)
if collection
before_save :before_save_collection_association
define_non_cyclic_method(save_method, reflection) { save_collection_association(reflection) }
# Doesn't use after_save as that would save associations added in after_create/after_update twice
after_create save_method
after_update save_method
elsif reflection.macro == :has_one
define_method(save_method) { save_has_one_association(reflection) }
# Configures two callbacks instead of a single after_save so that
# the model may rely on their execution order relative to its
# own callbacks.
#
# For example, given that after_creates run before after_saves, if
# we configured instead an after_save there would be no way to fire
# a custom after_create callback after the child association gets
# created.
after_create save_method
after_update save_method
else
define_non_cyclic_method(save_method, reflection) { save_belongs_to_association(reflection) }
before_save save_method
end
end
if reflection.validate? && !method_defined?(validation_method)
method = (collection ? :validate_collection_association : :validate_single_association)
define_non_cyclic_method(validation_method, reflection) { send(method, reflection) }
validate validation_method
end
end
end
# Reloads the attributes of the object as usual and clears <tt>marked_for_destruction</tt> flag.
def reload(options = nil)
@marked_for_destruction = false
super
end
# Marks this record to be destroyed as part of the parents save transaction.
# This does _not_ actually destroy the record instantly, rather child record will be destroyed
# when <tt>parent.save</tt> is called.
#
# Only useful if the <tt>:autosave</tt> option on the parent is enabled for this associated model.
def mark_for_destruction
@marked_for_destruction = true
end
# Returns whether or not this record will be destroyed as part of the parents save transaction.
#
# Only useful if the <tt>:autosave</tt> option on the parent is enabled for this associated model.
def marked_for_destruction?
@marked_for_destruction
end
# Returns whether or not this record has been changed in any way (including whether
# any of its nested autosave associations are likewise changed)
def changed_for_autosave?
new_record? || changed? || marked_for_destruction? || nested_records_changed_for_autosave?
end
private
# Returns the record for an association collection that should be validated
# or saved. If +autosave+ is +false+ only new records will be returned,
# unless the parent is/was a new record itself.
def associated_records_to_validate_or_save(association, new_record, autosave)
if new_record
association && association.target
elsif autosave
association.target.find_all { |record| record.changed_for_autosave? }
else
association.target.find_all { |record| record.new_record? }
end
end
# go through nested autosave associations that are loaded in memory (without loading
# any new ones), and return true if is changed for autosave
def nested_records_changed_for_autosave?
self.class.reflect_on_all_autosave_associations.any? do |reflection|
association = association_instance_get(reflection.name)
association && Array.wrap(association.target).any? { |a| a.changed_for_autosave? }
end
end
# Validate the association if <tt>:validate</tt> or <tt>:autosave</tt> is
# turned on for the association.
def validate_single_association(reflection)
association = association_instance_get(reflection.name)
record = association && association.reader
association_valid?(reflection, record) if record
end
# Validate the associated records if <tt>:validate</tt> or
# <tt>:autosave</tt> is turned on for the association specified by
# +reflection+.
def validate_collection_association(reflection)
if association = association_instance_get(reflection.name)
if records = associated_records_to_validate_or_save(association, new_record?, reflection.options[:autosave])
records.each { |record| association_valid?(reflection, record) }
end
end
end
# Returns whether or not the association is valid and applies any errors to
# the parent, <tt>self</tt>, if it wasn't. Skips any <tt>:autosave</tt>
# enabled records if they're marked_for_destruction? or destroyed.
def association_valid?(reflection, record)
return true if record.destroyed? || record.marked_for_destruction?
unless valid = record.valid?(validation_context)
if reflection.options[:autosave]
record.errors.each do |attribute, message|
attribute = "#{reflection.name}.#{attribute}"
errors[attribute] << message
errors[attribute].uniq!
end
else
errors.add(reflection.name)
end
end
valid
end
# Is used as a before_save callback to check while saving a collection
# association whether or not the parent was a new record before saving.
def before_save_collection_association
@new_record_before_save = new_record?
true
end
# Saves any new associated records, or all loaded autosave associations if
# <tt>:autosave</tt> is enabled on the association.
#
# In addition, it destroys all children that were marked for destruction
# with mark_for_destruction.
#
# This all happens inside a transaction, _if_ the Transactions module is included into
# ActiveRecord::Base after the AutosaveAssociation module, which it does by default.
def save_collection_association(reflection)
if association = association_instance_get(reflection.name)
autosave = reflection.options[:autosave]
if records = associated_records_to_validate_or_save(association, @new_record_before_save, autosave)
records_to_destroy = []
records.each do |record|
next if record.destroyed?
saved = true
if autosave && record.marked_for_destruction?
records_to_destroy << record
elsif autosave != false && (@new_record_before_save || record.new_record?)
if autosave
saved = association.insert_record(record, false)
else
association.insert_record(record) unless reflection.nested?
end
elsif autosave
saved = record.save(:validate => false)
end
raise ActiveRecord::Rollback unless saved
end
records_to_destroy.each do |record|
association.destroy(record)
end
end
# reconstruct the scope now that we know the owner's id
association.send(:reset_scope) if association.respond_to?(:reset_scope)
end
end
# Saves the associated record if it's new or <tt>:autosave</tt> is enabled
# on the association.
#
# In addition, it will destroy the association if it was marked for
# destruction with mark_for_destruction.
#
# This all happens inside a transaction, _if_ the Transactions module is included into
# ActiveRecord::Base after the AutosaveAssociation module, which it does by default.
def save_has_one_association(reflection)
association = association_instance_get(reflection.name)
record = association && association.load_target
if record && !record.destroyed?
autosave = reflection.options[:autosave]
if autosave && record.marked_for_destruction?
record.destroy
else
key = reflection.options[:primary_key] ? send(reflection.options[:primary_key]) : id
if autosave != false && (new_record? || record.new_record? || record[reflection.foreign_key] != key || autosave)
unless reflection.through_reflection
record[reflection.foreign_key] = key
end
saved = record.save(:validate => !autosave)
raise ActiveRecord::Rollback if !saved && autosave
saved
end
end
end
end
# Saves the associated record if it's new or <tt>:autosave</tt> is enabled.
#
# In addition, it will destroy the association if it was marked for destruction.
def save_belongs_to_association(reflection)
association = association_instance_get(reflection.name)
record = association && association.load_target
if record && !record.destroyed?
autosave = reflection.options[:autosave]
if autosave && record.marked_for_destruction?
record.destroy
elsif autosave != false
saved = record.save(:validate => !autosave) if record.new_record? || (autosave && record.changed_for_autosave?)
if association.updated?
association_id = record.send(reflection.options[:primary_key] || :id)
self[reflection.foreign_key] = association_id
association.loaded!
end
saved if autosave
end
end
end
end
end
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