jeditable

_properties.html.erb:
<dd class="edit_bpm editable"><%= song.try(:bpm) || '---' %></dd>

songs_controller.rb:
def pupdate
  #update only one attribute
  #used for inplace edit
  a = params[:song].first
  @song.update_attribute a[0], a[1]
  respond_with @song, location: band_song_url(@band, @song) do |format|
    format.js { render text: @song.send(a[0]) }
  end
end

songs.js:
$(function() {
  var set_editables = function() {
    //http://www.appelsiini.net/projects/jeditable
    /*** song bpm ***/
    var song_url = "/bands/" + gon.band_id + "/songs/" + gon.song_id + "/pupdate.js";
    $('.edit_bpm').editable(song_url, {
      tooltip : 'click to edit...',
      cancel  : 'cancel',
      submit  : 'save',
      select  : false,
      method  : 'PUT',
      name    : 'song[bpm]',
      placeholder: '---'
    });
  };
    
  set_editables();
});