how to get Select2 events on AngularJS

im using angularjs with select2 for application dropdowns, but i cannot figure how to get the change event or some other, inside my Controller.

is there some way to declare the eventhandler function via attribute?, like ui-select2 data-on-somethinghappened="fnx"?

or instead on my configuration? like:

appXpto.value('ui.config', {
    select2: {
        placeholder: 'Please select a value..',
        onsomethinghappened:function(e){ ... }
    }
});

thanks in advance