jquery plugin, boolean callback parameter

I am trying to pass a boolean parameter to a callback from inside a jquery plugin but parameter is always undefined.

The onSwitch callback parameter should alternate between true and false each time the link is clicked. Using a debugger I can see that the value passed to callback call function is properly defined as true or false but inside the callback implementation it turns to undefined.

I have tried looking at several other similar questions like this this and this but cannot seem to get this to work.

This is my plugin definition:

(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));

HTML:

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

plugin initialization:

$("#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");
    }
});

I have created a jsfiddle of the problem here.