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module ActiveRecord
module NestedAttributes #:nodoc:
def self.included(base)
base.extend(ClassMethods)
base.class_inheritable_accessor :reject_new_nested_attributes_procs, :instance_writer => false
base.reject_new_nested_attributes_procs = {}
end
# == Nested Attributes
#
# Nested attributes allow you to save attributes on associated records
# through the parent. By default nested attribute updating is turned off,
# you can enable it using the accepts_nested_attributes_for class method.
# When you enable nested attributes an attribute writer is defined on
# the model.
#
# The attribute writer is named after the association, which means that
# in the following example, two new methods are added to your model:
# <tt>author_attributes=(attributes)</tt> and
# <tt>pages_attributes=(attributes)</tt>.
#
# class Book < ActiveRecord::Base
# has_one :author
# has_many :pages
#
# accepts_nested_attributes_for :author, :pages
# end
#
# Note that the <tt>:autosave</tt> option is automatically enabled on every
# association that accepts_nested_attributes_for is used for.
#
# === One-to-one
#
# Consider a Member model that has one Avatar:
#
# class Member < ActiveRecord::Base
# has_one :avatar
# accepts_nested_attributes_for :avatar
# end
#
# Enabling nested attributes on a one-to-one association allows you to
# create the member and avatar in one go:
#
# params = { 'member' => { 'name' => 'Jack', 'avatar_attributes' => { 'icon' => 'smiling' } } }
# member = Member.create(params)
# member.avatar.icon #=> 'smiling'
#
# It also allows you to update the avatar through the member:
#
# params = { 'member' => { 'avatar_attributes' => { 'icon' => 'sad' } } }
# member.update_attributes params['member']
# member.avatar.icon #=> 'sad'
#
# By default you will only be able to set and update attributes on the
# associated model. If you want to destroy the associated model through the
# attributes hash, you have to enable it first using the
# <tt>:allow_destroy</tt> option.
#
# class Member < ActiveRecord::Base
# has_one :avatar
# accepts_nested_attributes_for :avatar, :allow_destroy => true
# end
#
# Now, when you add the <tt>_delete</tt> key to the attributes hash, with a
# value that evaluates to +true+, you will destroy the associated model:
#
# member.avatar_attributes = { '_delete' => '1' }
# member.avatar.marked_for_destruction? # => true
# member.save
# member.avatar #=> nil
#
# Note that the model will _not_ be destroyed until the parent is saved.
#
# === One-to-many
#
# Consider a member that has a number of posts:
#
# class Member < ActiveRecord::Base
# has_many :posts
# accepts_nested_attributes_for :posts, :reject_if => proc { |attributes| attributes['title'].blank? }
# end
#
# You can now set or update attributes on an associated post model through
# the attribute hash.
#
# For each key in the hash that starts with the string 'new' a new model
# will be instantiated. When the proc given with the <tt>:reject_if</tt>
# option evaluates to +false+ for a certain attribute hash no record will
# be built for that hash.
#
# params = { 'member' => {
# 'name' => 'joe', 'posts_attributes' => {
# 'new_12345' => { 'title' => 'Kari, the awesome Ruby documentation browser!' },
# 'new_54321' => { 'title' => 'The egalitarian assumption of the modern citizen' },
# 'new_67890' => { 'title' => '' } # This one matches the :reject_if proc and will not be instantiated.
# }
# }}
#
# member = Member.create(params['member'])
# member.posts.length #=> 2
# member.posts.first.title #=> 'Kari, the awesome Ruby documentation browser!'
# member.posts.second.title #=> 'The egalitarian assumption of the modern citizen'
#
# When the key for post attributes is an integer, the associated post with
# that ID will be updated:
#
# member.attributes = {
# 'name' => 'Joe',
# 'posts_attributes' => {
# '1' => { 'title' => '[UPDATED] An, as of yet, undisclosed awesome Ruby documentation browser!' },
# '2' => { 'title' => '[UPDATED] other post' }
# }
# }
#
# By default the associated models are protected from being destroyed. If
# you want to destroy any of the associated models through the attributes
# hash, you have to enable it first using the <tt>:allow_destroy</tt>
# option.
#
# This will allow you to specify which models to destroy in the attributes
# hash by setting the '_delete' attribute to a value that evaluates to
# +true+:
#
# class Member < ActiveRecord::Base
# has_many :posts
# accepts_nested_attributes_for :posts, :allow_destroy => true
# end
#
# params = {'member' => { 'name' => 'joe', 'posts_attributes' => {
# '2' => { '_delete' => '1' }
# }}}
# member.attributes = params['member']
# member.posts.detect { |p| p.id == 2 }.marked_for_destruction? # => true
# member.posts.length #=> 2
# member.save
# member.posts.length # => 1
#
# === Saving
#
# All changes to models, including the destruction of those marked for
# destruction, are saved and destroyed automatically and atomically when
# the parent model is saved. This happens inside the transaction initiated
# by the parents save method. See ActiveRecord::AutosaveAssociation.
module ClassMethods
# Defines an attributes writer for the specified association(s).
#
# Supported options:
# [:allow_destroy]
# If true, destroys any members from the attributes hash with a
# <tt>_delete</tt> key and a value that converts to +true+
# (eg. 1, '1', true, or 'true'). This option is off by default.
# [:reject_if]
# Allows you to specify a Proc that checks whether a record should be
# built for a certain attribute hash. The hash is passed to the Proc
# and the Proc should return either +true+ or +false+. When no Proc
# is specified a record will be built for all attribute hashes.
#
# Examples:
# accepts_nested_attributes_for :avatar
# accepts_nested_attributes_for :avatar, :allow_destroy => true
# accepts_nested_attributes_for :avatar, :reject_if => proc { ... }
# accepts_nested_attributes_for :avatar, :posts, :allow_destroy => true, :reject_if => proc { ... }
def accepts_nested_attributes_for(*attr_names)
options = { :allow_destroy => false }
options.update(attr_names.extract_options!)
options.assert_valid_keys(:allow_destroy, :reject_if)
attr_names.each do |association_name|
if reflection = reflect_on_association(association_name)
type = case reflection.macro
when :has_one, :belongs_to
:one_to_one
when :has_many, :has_and_belongs_to_many
:collection
end
reflection.options[:autosave] = true
self.reject_new_nested_attributes_procs[association_name.to_sym] = options[:reject_if]
# def pirate_attributes=(attributes)
# assign_nested_attributes_for_one_to_one_association(:pirate, attributes, false)
# end
class_eval %{
def #{association_name}_attributes=(attributes)
assign_nested_attributes_for_#{type}_association(:#{association_name}, attributes, #{options[:allow_destroy]})
end
}, __FILE__, __LINE__
else
raise ArgumentError, "No association found for name `#{association_name}'. Has it been defined yet?"
end
end
end
end
# Returns ActiveRecord::AutosaveAssociation::marked_for_destruction?
# It's used in conjunction with fields_for to build a form element
# for the destruction of this association.
#
# See ActionView::Helpers::FormHelper::fields_for for more info.
def _delete
marked_for_destruction?
end
private
# Assigns the given attributes to the association. An association will be
# build if it doesn't exist yet.
def assign_nested_attributes_for_one_to_one_association(association_name, attributes, allow_destroy)
if should_destroy_nested_attributes_record?(allow_destroy, attributes)
send(association_name).mark_for_destruction
else
(send(association_name) || send("build_#{association_name}")).attributes = attributes
end
end
# Assigns the given attributes to the collection association.
#
# Keys containing an ID for an associated record will update that record.
# Keys starting with <tt>new</tt> will instantiate a new record for that
# association.
#
# For example:
#
# assign_nested_attributes_for_collection_association(:people, {
# '1' => { 'name' => 'Peter' },
# 'new_43' => { 'name' => 'John' }
# })
#
# Will update the name of the Person with ID 1 and create a new associated
# person with the name 'John'.
def assign_nested_attributes_for_collection_association(association_name, attributes, allow_destroy)
unless attributes.is_a?(Hash)
raise ArgumentError, "Hash expected, got #{attributes.class.name} (#{attributes.inspect})"
end
# Make sure any new records sorted by their id before they're build.
sorted_by_id = attributes.sort_by { |id, _| id.is_a?(String) ? id.sub(/^new_/, '').to_i : id }
sorted_by_id.each do |id, record_attributes|
if id.acts_like?(:string) && id.starts_with?('new_')
build_new_nested_attributes_record(association_name, record_attributes)
else
assign_to_or_destroy_nested_attributes_record(association_name, id, record_attributes, allow_destroy)
end
end
end
# Returns +true+ if <tt>allow_destroy</tt> is enabled and the attributes
# contains a truthy value for the key <tt>'_delete'</tt>.
#
# It will _always_ remove the <tt>'_delete'</tt> key, if present.
def should_destroy_nested_attributes_record?(allow_destroy, attributes)
ConnectionAdapters::Column.value_to_boolean(attributes.delete('_delete')) && allow_destroy
end
# Builds a new record with the given attributes.
#
# If a <tt>:reject_if</tt> proc exists for this association, it will be
# called with the attributes as its argument. If the proc returns a truthy
# value, the record is _not_ build.
def build_new_nested_attributes_record(association_name, attributes)
if reject_proc = self.class.reject_new_nested_attributes_procs[association_name]
return if reject_proc.call(attributes)
end
send(association_name).build(attributes)
end
# Assigns the attributes to the record specified by +id+. Or marks it for
# destruction if #should_destroy_nested_attributes_record? returns +true+.
def assign_to_or_destroy_nested_attributes_record(association_name, id, attributes, allow_destroy)
record = send(association_name).detect { |record| record.id == id.to_i }
if should_destroy_nested_attributes_record?(allow_destroy, attributes)
record.mark_for_destruction
else
record.attributes = attributes
end
end
end
end
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