Select Form for Embedded model with rails 4 mongoid - ruby-on-rails

Question

I have a embedded model, Document in the embedded model can only be created by the admin, but users can select in form the value that they want
class User
include Mongoid::Document
embeds_one :state_model, class_name: "state_model", cascade_callbacks: true
accepts_nested_attributes_for :state_model
attr_accessor :current_password, :job_title_str, :state_model_id
convert_id_to_object :state_model_id, :state_model
end
class UsersController << ApplicationController
def update_params
params.require(:user).permit(:state_model_id)
end
end
module ConvertIdToObject
extend ActiveSupport::Concern
module ClassMethods
def convert_id_to_object(id, object)
id, object = id, object
if StateModel.by_id(id).present?
object = StateModel.by_id(id)
else
end
end
end
end
class StateModel
include Mongoid::Document
field :name, type: String, localize: true
field :value, type: String
scope :by_value, -> (value){ where({:value => value}) unless value == ''}
scope :by_id, -> (id){ where({:id => id}) unless id == ''}
embedded_in :user
validates :name, presence: true, uniqueness: true
validates :value, presence: true, uniqueness: true
end
= simple_form_for user do |f|
= f.input :state_model_id , collection: state_collection
= f.button :submit
Post:
{"utf8"=>"✓",
"_method"=>"patch",
"authenticity_token"=>"3/pmSUHrKRx56ycbraKYL+mEuAiS9QlwWt/bTglgsio=",
"user"=>{"state_model_id"=>"5612cb074d6f722582050000"},
"commit"=>"Update User",
"id"=>"bowtch"}
End I have a Notimplemented error raised by my usercontroller Like if don't accept state_model_id as a param ... I'm stuck here ...