フォームに入力された住所から緯度経度を取得してPOST

_form.html.haml

%script{type: "text/javascript", src: "http://maps.google.com/maps/api/js?sensor=false"}
:javascript
  function addGeocode(){
    var geocoder = new google.maps.Geocoder();
    geocoder.geocode({'address': document.getElementById('place_address').value}, function(results, status) {
      if (status == google.maps.GeocoderStatus.OK) {
        // 緯度、経度を取得
        var lat = results[0].geometry.location.lat();
        var lng = results[0].geometry.location.lng();
        // 緯度、経度をhiddenパラメータを追加
        document.getElementById('location_latitude').value = lat;
        document.getElementById('location_longitude').value = lng;
        // フォームを送信
        document.place_form.submit();
      } else {
        alert("Geocode was not successful for the following reason: " + status);
      }
    });
  }

= form_for @place, html:{name:'place_form'} do |f|
  -if @place.errors.any?
    #error_explanation
      %h2= "#{pluralize(@place.errors.count, "error")} prohibited this place from being saved:"
      %ul
        - @place.errors.full_messages.each do |msg|
          %li= msg

  .field
    = f.label :name
    = f.text_field :name
  .field
    = f.label :address
    = f.text_field :address
  = fields_for @place.location do |location_fields|
    .hidden_field  
      = location_fields.hidden_field :latitude
    .hidden_field
      = location_fields.hidden_field :longitude
  .button
    %input{type: 'button', value: 'Save', onclick: 'addGeocode()'}