Add support for nested object forms to ActiveRecord and the helpers in ActionPack

Signed-Off-By: Michael Koziarski <michael@koziarski.com>

[#1202 state:committed]

1 files changed, 279 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/nested_attributes.rb b/activerecord/lib/active_record/nested_attributes.rb
new file mode 100644
index 0000000000..8bfdadd0e3
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+++ b/activerecord/lib/active_record/nested_attributes.rb
@@ -0,0 +1,279 @@
+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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