gistfile1.js

YUI().use('model', 'view', function (Y) {

    Y.FooView = Y.Base.create('fooView', Y.View, [], {
        initializer: function () {
            var model = this.get('model');

            // If this view was constructed with a `model` make its events 
            // bubble up.
            model && model.addTarget(this);

            // Listen for this view's `model` to be switched with a new `model`.
            this.after('modelChange', this._afterModelChange);

            // Listen for this view's current `model` to have its `bar` 
            // attribute changed. This decouples the responding to the event 
            // from the publisher of the event. Therefore this event 
            // subscription still works even if this view's `model` changes.
            this.after('model:barChange', this._reRenderBar, this);
        },

        _afterModelChange: function (e) {
            // Remove old `model` as a bubble target, and make the new `model` a
            // bubble target of this view. This is what makes this view not care
            // which `model` fires its `barChange` event.
            e.prevVal && e.prevVal.removeTarget(this);
            e.newVal && e.newVal.addTarget(this);

            console.log('View\'s `model` changed.');
        },

        _reRenderBar: function (e) {
            // Reflect the `bar` attribute's state change in the DOM.
            console.log('Model\'s `bar` attribute changed.');
        }
    });

    var model1 = new Y.Model(),
        model2 = new Y.Model(),
        view   = new Y.FooView({model: model1});

    model1.set('bar', 'bla');     // => Model's `bar` attribute changed.
    model2.set('bar', 'bla');
    view.set('model', model2);    // => View's `model` changed.
    
    // `model1` has been "detached" from the `view`, therefore its events no 
    // longer bubble to the `view`.
    model1.set('bar', 'bla bla');

    // Now that `model2` is attached to the `view`, its `barChange` event
    // bubbles to the `view`.
    model2.set('bar', 'bla bla'); // => Model's `bar` attribute changed.

});