Has_one Association breaking in Edit - ruby-on-rails

Question

I have a nested form using the cocoon gem that gests 5 classes deep. They are all belongs_to and has_many except one that is the 2nd to most nested class with a has_one and belongs_to association. Whenever I edit it, it gets deleted and recreates an instance (not what I want) any ideas?
class FirmwaresController < ApplicationController
def index
#firmwares = Firmware.all
end
def new
#firmware = Firmware.new
end
def edit
#firmware = Firmware.find(params[:id])
end
end
class Setting < ActiveRecord::Base
belongs_to :menu_item
has_many :selections, dependent: :destroy
has_many :dependencies
attr_accessible :kind, :name, :placement, :selections_attributes
accepts_nested_attributes_for :selections, reject_if: :all_blank, allow_destroy: true
validates_presence_of :kind
end
class MenuItem < ActiveRecord::Base
belongs_to :menu
belongs_to :dependency
has_one :setting, dependent: :destroy
attr_accessible :dependency_id, :menu_for, :name, :placement, :setting_attributes
accepts_nested_attributes_for :setting, reject_if: :all_blank, allow_destroy: true
validates_presence_of :name
end
_menu_items.html.haml
.row-fluid
.input-prepend
= f.input :name, label: "Menu Item Name"
.input-append
= f.input :placement, label: "Order in Menu (X.Y)", as: :string
= f.simple_fields_for :setting do |settings_form|
= render 'setting_fields', f: settings_form
%p
= link_to_add_association "Has Setting?", f, :setting, class: "btn btn-primary btn-small add_setting_link"
= link_to_remove_association 'Remove Menu Item', f, class: "btn btn-danger btn-small remove_menu_item"
_setting_fields.html.haml
.row-fluid
.input-prepend
= f.input :kind, label: "Type", collection: setting_kinds, input_html: {class: "setting_type"}
.input-append
= link_to_remove_association 'Remove Setting', f, class: 'btn btn-danger btn-small remove_setting_link'
.setting_selection{style: "display: none;"}
= f.simple_fields_for :selections do |selections_form|
= render 'selection_fields', f: selections_form
%p= link_to_add_association 'Add Selection Option', f, :selections, class: "btn btn-primary btn-small"

Answer 1

I assume the has_one association you're referring to is the has_one :setting in MenuItem. If so, you might try adding update_only: true to your accepts_nested_attributes_for :setting options. From the documentation (emphasis mine):
By default the :update_only option is false and the nested attributes are used to update the existing record only if they include the record's :id value. Otherwise a new record will be instantiated and used to replace the existing one. However if the :update_only option is true, the nested attributes are used to update the record’s attributes always, regardless of whether the :id is present.

Answer 2

This question is old, but this could help some people:
The reason the association was always recreated for me, was that I had forgotten to include :id in the permitted parameters of phone_number_attributes! If you forget to do that, rails wont get the id and will recreate a new record to replace the old one.
def user_params
params.require(:user).permit(
:avatar,
:remove_avatar,
{ id_photo_attributes: [:photo, :remove_photo] },
{ phone_number_attributes: [:id, :phone_number] } # dont forget :id here!
)
end