plugin callback parameter not working

HTML

<a id="switchTest" href="#">switch</a>

JavaScript

(function ($) {
    $.fn.switcherButton = function (options) {
        // Set the default options
        var settings = $.extend({},$.fn.switcherButton.defaults, options);

        this.click(function () {
            $.fn.switcherButton.switched = !$.fn.switcherButton.switched;
            settings.onSwitch.call($.fn.switcherButton.switched);
        });
        return this;
    };
    // Plugin defaults – added as a property on our plugin function.
    $.fn.switcherButton.defaults = {
        onSwitch: function() {}
    };
    $.fn.switcherButton.switched = false;
}(jQuery));

$("#switchTest").switcherButton({
    onSwitch: function(switched){
        if(typeof switched === "undefined")
            alert("callback param = undefined");
        else
            if(switched)
                alert("callback param = true");
            else
                alert("callback param = false");
    }
});