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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.id # => 2
# member.avatar.icon # => 'smiling'
#
# It also allows you to update the avatar through the member:
#
# params = { :member' => { :avatar_attributes => { :id => '2', :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 = { :id => '2', :_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
# end
#
# You can now set or update attributes on an associated post model through
# the attribute hash.
#
# For each hash that does _not_ have an <tt>id</tt> key a new record will
# be instantiated, unless the hash also contains a <tt>_delete</tt> key
# that evaluates to +true+.
#
# params = { :member => {
# :name => 'joe', :posts_attributes => [
# { :title => 'Kari, the awesome Ruby documentation browser!' },
# { :title => 'The egalitarian assumption of the modern citizen' },
# { :title => '', :_delete => '1' } # this will be ignored
# ]
# }}
#
# 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'
#
# You may also set a :reject_if proc to silently ignore any new record
# hashes if they fail to pass your criteria. For example, the previous
# example could be rewritten as:
#
# class Member < ActiveRecord::Base
# has_many :posts
# accepts_nested_attributes_for :posts, :reject_if => proc { |attributes| attributes['title'].blank? }
# end
#
# params = { :member => {
# :name => 'joe', :posts_attributes => [
# { :title => 'Kari, the awesome Ruby documentation browser!' },
# { :title => 'The egalitarian assumption of the modern citizen' },
# { :title => '' } # this will be ignored because of the :reject_if proc
# ]
# }}
#
# 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'
#
# If the hash contains an <tt>id</tt> key that matches an already
# associated record, the matching record will be modified:
#
# member.attributes = {
# :name => 'Joe',
# :posts_attributes => [
# { :id => 1, :title => '[UPDATED] An, as of yet, undisclosed awesome Ruby documentation browser!' },
# { :id => 2, :title => '[UPDATED] other post' }
# ]
# }
#
# member.posts.first.title # => '[UPDATED] An, as of yet, undisclosed awesome Ruby documentation browser!'
# member.posts.second.title # => '[UPDATED] other post'
#
# By default the associated records are protected from being destroyed. If
# you want to destroy any of the associated records through the attributes
# hash, you have to enable it first using the <tt>:allow_destroy</tt>
# option. This will allow you to also use the <tt>_delete</tt> key to
# destroy existing records:
#
# class Member < ActiveRecord::Base
# has_many :posts
# accepts_nested_attributes_for :posts, :allow_destroy => true
# end
#
# params = { :member => {
# :posts_attributes => [{ :id => '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). If you
# are using <tt>attr_protected</tt> or <tt>attr_accessible</tt>, then you
# will need to add the attribute writer to the allowed list.
#
# Supported options:
# [:allow_destroy]
# If true, destroys any members from the attributes hash with a
# <tt>_delete</tt> key and a value that evaluates 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 that
# do not have a <tt>_delete</tt> that evaluates to true.
#
# Examples:
# # creates avatar_attributes=
# accepts_nested_attributes_for :avatar, :reject_if => proc { |attributes| attributes['name'].blank? }
# # creates avatar_attributes= and posts_attributes=
# accepts_nested_attributes_for :avatar, :posts, :allow_destroy => true
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
# Attribute hash keys that should not be assigned as normal attributes.
# These hash keys are nested attributes implementation details.
UNASSIGNABLE_KEYS = %w{ id _delete }
# Assigns the given attributes to the association.
#
# If the given attributes include an <tt>:id</tt> that matches the existing
# record’s id, then the existing record will be modified. Otherwise a new
# record will be built.
#
# If the given attributes include a matching <tt>:id</tt> attribute _and_ a
# <tt>:_delete</tt> key set to a truthy value, then the existing record
# will be marked for destruction.
def assign_nested_attributes_for_one_to_one_association(association_name, attributes, allow_destroy)
attributes = attributes.stringify_keys
if attributes['id'].blank?
unless reject_new_record?(association_name, attributes)
send("build_#{association_name}", attributes.except(*UNASSIGNABLE_KEYS))
end
elsif (existing_record = send(association_name)) && existing_record.id.to_s == attributes['id'].to_s
assign_to_or_mark_for_destruction(existing_record, attributes, allow_destroy)
end
end
# Assigns the given attributes to the collection association.
#
# Hashes with an <tt>:id</tt> value matching an existing associated record
# will update that record. Hashes without an <tt>:id</tt> value will build
# a new record for the association. Hashes with a matching <tt>:id</tt>
# value and a <tt>:_delete</tt> key set to a truthy value will mark the
# matched record for destruction.
#
# For example:
#
# assign_nested_attributes_for_collection_association(:people, {
# '1' => { :id => '1', :name => 'Peter' },
# '2' => { :name => 'John' },
# '3' => { :id => '2', :_delete => true }
# })
#
# Will update the name of the Person with ID 1, build a new associated
# person with the name `John', and mark the associatied Person with ID 2
# for destruction.
#
# Also accepts an Array of attribute hashes:
#
# assign_nested_attributes_for_collection_association(:people, [
# { :id => '1', :name => 'Peter' },
# { :name => 'John' },
# { :id => '2', :_delete => true }
# ])
def assign_nested_attributes_for_collection_association(association_name, attributes_collection, allow_destroy)
unless attributes_collection.is_a?(Hash) || attributes_collection.is_a?(Array)
raise ArgumentError, "Hash or Array expected, got #{attributes_collection.class.name} (#{attributes_collection.inspect})"
end
if attributes_collection.is_a? Hash
attributes_collection = attributes_collection.sort_by { |index, _| index.to_i }.map { |_, attributes| attributes }
end
attributes_collection.each do |attributes|
attributes = attributes.stringify_keys
if attributes['id'].blank?
unless reject_new_record?(association_name, attributes)
send(association_name).build(attributes.except(*UNASSIGNABLE_KEYS))
end
elsif existing_record = send(association_name).detect { |record| record.id.to_s == attributes['id'].to_s }
assign_to_or_mark_for_destruction(existing_record, attributes, allow_destroy)
end
end
end
# Updates a record with the +attributes+ or marks it for destruction if
# +allow_destroy+ is +true+ and has_delete_flag? returns +true+.
def assign_to_or_mark_for_destruction(record, attributes, allow_destroy)
if has_delete_flag?(attributes) && allow_destroy
record.mark_for_destruction
else
record.attributes = attributes.except(*UNASSIGNABLE_KEYS)
end
end
# Determines if a hash contains a truthy _delete key.
def has_delete_flag?(hash)
ConnectionAdapters::Column.value_to_boolean hash['_delete']
end
# Determines if a new record should be build by checking for
# has_delete_flag? or if a <tt>:reject_if</tt> proc exists for this
# association and evaluates to +true+.
def reject_new_record?(association_name, attributes)
has_delete_flag?(attributes) ||
self.class.reject_new_nested_attributes_procs[association_name].try(:call, attributes)
end
end
end
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