chainselect ruby on rails, problem with javascript [duplicate]

I try to make a select with a form.

Form

<%= simple_form_for(@persona) do |f| %>
  <%= f.error_notification %>

  <div class="form-inputs">

    <%= f.input :identificacion %>

    <%= f.input :nombre %>
    <%= f.input :email %>

  </div>

 <div class="row">
  <div class="col-md-4">
       <label>Pais</label>
    <%= select_tag "pais", options_from_collection_for_select(@paises, "id", "name" ), class: "form-control", :include_blank => "Seleccione Pais" %>

  </div>
  <div class="col-md-3">
       <label>Departamento</label>
       <%= select_tag "departamento", "<option value="">Seleccione departamento</option>".html_safe, class: "form-control" %>
  </div>
  <div class="col-md-2">
    <%= select_tag "persona[municipio_id]", "<option value="">Seleccione Municipio</option>".html_safe,
   class: "form-control" %>

</div>
<div class="form-actions">
    <%= f.button :submit %>
  </div>
</div>
<% end %>

JavaScript

$(document).on('turbolinks:load', function(){

   // Empieza codigo para select anidados
   $("#pais").change(function(event, data) {

    var id_pais = $('select#pais :selected').val();
    $.ajax({
    url: '/personas/select_departamento',
    dataType: "JSON",
    type: 'GET',
    data: { idpais: id_pais },
    success: function(data) {
        var $select = $('#departamento');
        $select.empty().append('<option value="">Seleccione Departamento</option>');
        $(data).each(function (index, o) {    
        var $option = $("<option/>").attr("value", o.id).text(o.name);
        $select.append($option);
        });      
    }
    });
    // inicializar los selects
    var $select = $('#persona_municipio_id');
    $select.empty().append('<option value="">Seleccione Municipio</option>');
  });

  $("#departamento").change(function(event, data) {
    var id_departamento =  $('select#departamento :selected').val();
    $.ajax({
    url: '/personas/select_municipio',
    dataType: "JSON",
    type: 'GET',
    data: { iddepartamento: id_departamento },
    success: function(data) {
        var $select = $('#persona_municipio_id');
        $select.empty().append('<option value="">Seleccione Municipio</option>');
        $(data).each(function (index, o) {    
        var $option = $("<option/>").attr("value", o.id).text(o.name);
        $select.append($option);
        });      
    }
    });

  });

  // Termina codigo para select anidados  

});

In Controller

class PersonasController < ApplicationController
  before_action :set_persona, only: [:show, :edit, :update, :destroy]

  # GET /personas
  # GET /personas.json
  def index
    @personas = Persona.all
    @paises   = Pais.all
  end

 # select anidados
  def select_departamento
    rs = Departamento.where(:pais_id => params[:idpais]).order('name').all
    respond_to do |format|
    format.json {render json: rs }
    format.html
    end
  end

  def select_municipio
    rs = Municipio.where(:departamento_id => params[:iddepartamento]).order('name').all
    respond_to do |format|
    format.json {render json: rs }
    format.html
    end
  end

  # GET /personas/1
  # GET /personas/1.json
  def show
  end

  # GET /personas/new
  def new
    @persona = Persona.new
    @paises   = Pais.all
  end

  # GET /personas/1/edit
  def edit
  end

  # POST /personas
  # POST /personas.json
  def create
    @persona = Persona.new(persona_params)
    respond_to do |format|
      if @persona.save
        format.html { redirect_to @persona, notice: 'Persona was successfully created.' }
        format.json { render :show, status: :created, location: @persona }
      else
          @paises   = Pais.all
        format.html { render :new }
        format.json { render json: @persona.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /personas/1
  # PATCH/PUT /personas/1.json
  def update
    respond_to do |format|
      if @persona.update(persona_params)
        format.html { redirect_to @persona, notice: 'Persona was successfully updated.' }
        format.json { render :show, status: :ok, location: @persona }
      else
        format.html { render :edit }
        format.json { render json: @persona.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /personas/1
  # DELETE /personas/1.json
  def destroy
    @persona.destroy
    respond_to do |format|
      format.html { redirect_to personas_url, notice: 'Persona was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

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

    # Never trust parameters from the scary internet, only allow the white list through.
    def persona_params
      params.require(:persona).permit(:identificacion, :nombre, :email, :municipio_id)
    end
end

The select works.

Model

class Persona < ApplicationRecord
  belongs_to :municipio
end

This was an error that came up after adding save!

  

Validation failed: Municipality must exist

The table municipality there are saved data, one how organizes so that municipio_id receives the municipality id, I believe is where the problem is.

I'm just started and I'm passionate and I'm doing my best to improve and understand, thank you very much for the help.

already saves me but when it goes to load the show

** I get an error ** in the view shows

log