Nested Forms for Embedded Documents

Question

I have the following Models

cities(id, name, geo {lng,lat})

geo(lng,lat)

Cities Model

class City
  include Mongoid::Document
  include Mongoid::Timestamps

  field :name, type: String
  field :timezone, type: String
  field :slug, type: String

  belongs_to :region
  belongs_to :country

  embeds_one :geo_location
  accepts_nested_attributes_for :geo_location
end

Geo Locations Model

class GeoLocation
  include Mongoid::Document
  include Mongoid::Timestamps

  field :lng, type: String
  field :lat, type: String

  embedded_in :city
end

Cities Controller

class CitiesController < ApplicationController
  before_action :set_city, only: [:show, :edit, :update, :destroy]

  # GET /cities
  def index
    @cities = City.all
  end

  # GET /cities/1
  def show
  end

  # GET /cities/new
  def new
    @city = City.new
    @regions = Region.all.asc(:name)
    @countries = Country.all.asc(:name)
  end

  # GET /cities/1/edit
  def edit
    @regions = Region.all.asc(:name)
    @countries = Country.all.asc(:name)
  end

  # POST /cities
  def create
    @city = City.new(city_params)

    if @city.save
      redirect_to @city, notice: 'City was successfully created.'
    else
      render action: 'new'
    end
  end

  # PATCH/PUT /cities/1
  def update
    if @city.update(city_params)
      redirect_to @city, notice: 'City was successfully updated.'
    else
      render action: 'edit'
    end
  end

  # DELETE /cities/1
  def destroy
    @city.destroy
    redirect_to cities_url, notice: 'City was successfully destroyed.'
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_city
      @city = City.find(params[:id])
    end

    # Only allow a trusted parameter "white list" through.
    def city_params
      params.require(:city).permit(:name, :timezone, :region_id, :country_id, :slug, :geo_locations_attributes => [:id, :lag, :lat])
    end
end

Form:

<%= form_for(@city) do |f| %>
  <% if @city.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@city.errors.count, "error") %> prohibited this city from being saved:</h2>

      <ul>
      <% @city.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= f.label :name %><br>
    <%= f.text_field :name %>
  </div>
  <div class="field">
    <%= f.label :country %><br>
    <%= f.collection_select :country_id, @countries, :id, :name, :prompt => "Please Select" %>
  </div>
  <div class="field">
    <%= f.label :region %><br>
    <%= f.collection_select :region_id, @regions, :id, :name, :prompt => "Please Select" %>
  </div>
  <div class="field">
    <%= f.label :timezone %><br>
    <%= f.text_field :timezone %>
  </div>
  <div class="field">
    <%= f.label :slug %><br>
    <%= f.text_field :slug %>
  </div>

  <%= f.fields_for :geo_locations do |geo_location| %>
    <div class="field">
      <%= geo_location.label :lag %><br>
      <%= geo_location.text_field :lag %>
    </div>
    <div class="field">
      <%= geo_location.label :lat %><br>
      <%= geo_location.text_field :lat %>
    </div>
  <% end %>

  <div class="actions">
    <%= f.submit %>
  </div>
<% end %>

New View

<h1>New city</h1>

<%= render 'form' %>

<%= link_to 'Back', cities_path %>

The ERROR I am getting

Unpermitted parameters: geo_location

Answer 1

On controller, Replace your city_params method with this,

def city_params
  params.require(:city).permit(:name, :timezone, :region_id, :country_id, :slug, :geo_location_attributes => [:id, :lag, :lat])
end

On view, Replace this "f.fields_for :geo_locations" with "f.fields_for :geo_location"

Problem in geo_locations_attributes. It should be geo_location_attributes as this is one-to-one relationship.