Using meld.js in an function with ajax callback

I am trying to using meld.js in mean.io framework. It is easy and quick to use "before". But I got a problem while excuting an after advise in a function with an ajax callback. like this:

exports.test = function(req, res) {
    // ...
    $http({
        options, 
        function(result) {
            return res.send(200);
        }, 
        function(result){
            return res.send(400);
        }
    });
}

when I add this:

meld.after(obj, 'test', function(result) {
    console.log(result);
});

However I can only get undefined. Can anyone tell me how I can get the returned result inside the callback functions?