How to access the one of the chained functions in a plugin?

How can I access the one of the chained functions in a plugin?

this is my plugin, in which I need to return an appended element on the document.

(function($){

        $.fn.extend({ 

            selection: function(options) {

                var defaults = {
                    element:     "selection"
                }

                var options =  $.extend(defaults, options);
                var o = options;

                var $this = this;


               $this.function_1 = function(object)
                {
                    alert('function 1');

                }

                $this.function_2 = function(object)
                {
                    alert('function 2');
                }

                $(document.body).append("<div class='element'>Loading</div>");

                var element = $('.element');

                return element;

            }
        });

    })(jQuery);​

It should alerts 'function 2' when the button is clicked but it returns error on firefox.

Below is my jsffiddle,

http://jsfiddle.net/dm3ft/

One approach is to add an argument to the plugin function to pass method as string. Basics are taken from jQuery plugin authoring docs:

(function($) {

    var methods = {
        function_1: function(object) {
            alert('function 1');
        },
        function_2: function(object) {
            alert('function 2');
        }
    };


$.fn.selection = function(method, options) {

    return this.each(function(){

        $(this).click(function() {

              // Method calling logic
               if (methods[method]) {
                   return methods[method].apply(this, Array.prototype.slice.call(arguments, 1));
               } else if (typeof method === 'object' || !method) {
                   return methods.init.apply(this, arguments);
               } else {
                   $.error('Method ' + method + ' does not exist on jQuery.tooltip');
               }
          });
    });

})(jQuery);

Then to call plugin method:

  $('.chain-function').selection('function_2'/* optional options object*/);

DEMO: http://jsfiddle.net/dm3ft/1/

NOTE: It is important that you realize that this inside the plugin function is the DOM element and not confuse it with this being part of your class