[jQuery] "subclassing" ajaxForm

[jQuery] "subclassing" ajaxForm


When I try to do this, firebug does not alert me of anything wrong,
the form is posted normally (no ajax).
What mistake am I making?
// requires jquery.forms plugin
jQuery.fn.jsonForm = function(onSuccess) {
this.ajaxForm({
dataType: 'json',
success: function(data) {
if (data.Message) {
alert(data.Message); // my json reply always has these 2
fields
}
if (data.ActionUrl != null) {
top.location = data.ActionUrl;
}
if (onSuccess != null) {
onSuccess(data); // what if onSuccess has an empty
signature?
}
}
});
}
So I can call it like so:
    var onSuccess = function(data){
        $.each(data.Customer, function(i, item){
            $('#searchResultCustomers').append("<dd>"+ item.Name +"</dd>");
        });
    });
    $('.jsonFormCustomer').jsonForm(onSuccess);
How could I call jsonForm without a null param, too?
Help greatly appreciated!