var Messages = {
  onComplete: function(request, transport, json) {
    this.extractMessages(json);
  },
  onFailure: function(request, transport, json) {
    this.extractMessages(json);
  },
  extractMessages: function(json) {
    for (msgClass in json) {
      msgsOfClass = typeof( json[msgClass] ) == 'string' ? new Array(json[msgClass]) : json[msgClass];
      for (var i = 0; i < msgsOfClass.length; i++) {
        Growl4Rails.showGrowl({image_path:'/images/growl4rails/'+msgClass+'.png', title:msgClass, message:msgsOfClass[i]});
      }
    }
  }
};
Ajax.Responders.register(Messages);