A snippet from rsvp.js from my wedding site.

rsvp.js

Y.Model.prototype.promiseSave = function (options) {
    var model = this;

    return new Y.Promise(function (resolve, reject) {
        model.save(options, function (err, res) {
            return err ? reject(err) : resolve(res);
        });
    });
};

var app = new Y.App({
    container      : '#main',
    viewContainer  : '#main',
    contentSelector: '#main',
    linkSelector   : null,

    transitions: true,
    root       : '/rsvp/',

    views: {
        rsvp        : {type: Y.RsvpView},
        attending   : {type: Y.AttendingView},
        notAttending: {type: Y.NotAttendingView}
    }
});

app.invitation     = new Y.Invitation(YUI.Env.LE.invitation);
app.initialContent = Y.one('#main > [data-view]');

app.rsvp = function (isAttending) {
    var guests = this.invitation.get('guests'),
        saves  = [app.updateInvitation({rsvpd: true, send_paper: false})];

    guests.invoke('set', 'is_attending', isAttending);
    saves.push.apply(saves, guests.invoke('promiseSave'));

    Y.batch.apply(null, saves).then(function () {
        app.replace('');
    });
};

app.updateInvitation = function (updates) {
    this.invitation.setAttrs(updates);

    if (this.invitation.isModified()) {
        return this.invitation.promiseSave();
    }

    return Y.when(true);
};

app.on('*:rsvp', function (e) {
    this.rsvp(e.isAttending);
});