On "Views as components"

> Each view can include other ‘sub’ views, which can themselves include subviews and so on.

This is something that is missing from Backbone and it's something that always comes up, even when doing something as simple as a Todo list. In the Backbone Todo list example[1] you there are methods on the "parent view" (eg, the List view or the App view) to addOne and addAll (rendering the Item views).

So the concept of "sub views" is definitely needed but what I'd like to know, from SoundCloud's perspective, what were the arguments for/against implementing this functionality from within the templates and not from some place else, eg. the parent view's or the sub view's constructor (as a parent/child attribute) or initialize method.

> Each view is responsible for its own setup, events, data, and clean up.

Having already implemented the "sub views" concept it seems perfectly logical to allow a parent view to inherit DOM events from its children. Considering the Todo list example, and without using Backbone, how would you implement DOM events on the Todo items? You wouldn't bind events on each item's DOM element - that's just crazy. You would bind the events on the list (just once, for all items) and find a way to know on which item the event was triggered. In other words, you would use $('parent').on('event', 'child' ... ) and not $('child').bind.

It seems that with Backbone people have forgotten this practice, in a way similar to how people started using inefficient DOM selectors when jQuery came along.

So, when implementing the "sub view"/"parent view" concept, what would make perfect sense is to specify if the sub view's DOM events should be bounded on the parent view's DOM element. What I'd like to know is if SoundCloud has considered doing this and if yes why they have decided against it.

[1] http://documentcloud.github.com/backbone/examples/todos/todo...

>what were the arguments for/against implementing this functionality from within the templates and not from some place else

It is still quite possible for parent views to construct subviews and insert them into its own DOM at any time, but due to the nature of our views, many of them are UI components, and so it made sense to be able to define both the subview as well as its position at the same time. It makes writing a view with subviews very easy. You simply use the Handlebars helper exactly where you want that view and the rest is taken care of for you.

>You would bind the events on the list (just once, for all items) and find a way to know on which item the event was triggered.

Yes, that's a very common approach to handing DOM events, but it ran against our belief that views should be independent. If a view can only work in a particular situation (eg: nested inside a list which handles its events), then that creates hard dependencies between those two views and you can quickly get into a mess. Event delegation is definitely used in Next, but only at a per-view level. It is a sacrifice (I would posit that it's a minor sacrifice), but the benefits are highly independent and reusable views. We do take advantage of this, too: for example, if you look at the waveform in the player, and the miniature waveform in the header which shows your currently-playing sound (visible in the screenshot), that is the exact same view. Because they handle everything themselves, there was absolute minimum work needed to add that feature.

Thanks for the feedback and the interest, Nick.

Note that I'm just talking about our particular project: YMMV, and using event delegation in higher level views for your own project might provide bigger wins in terms of performance or maintainability.

It does indeed look very simple and easy but what I would be concerned about is that you have logic in your views that perhaps shouldn't be there. Your views are now dependent on the template language/parser you are using. Have you tried any other approaches that didn't work so well/easy before coming to this solution?

> If a view can only work in a particular situation (eg: nested inside a list which handles its events), then that creates hard dependencies between those two views and you can quickly get into a mess.

Agree. But how about having per view instance dependency instead of per view constructor. For example,

    <div class="listenNetwork__creator">
        {{view "views/user/user-badge" resource_id=user.id parent_view=this }}
    </div>

Thanks

    > This is something that is missing from Backbone 
    > and it's something that always comes up

    > You would bind the events on the list (just once, 
    > for all items) and find a way to know on which 
    > item the event was triggered.

That said, binding to individual elements isn't problematic unless you're truly doing too much of it. 20 songs each with their own bound callbacks would be fine, but 2,000 songs wouldn't be. When to delegate for performance follows the same reasoning as it would in a plain 'ol jQuery app, and is touched on briefly in the FAQ: http://backbonejs.org/#FAQ-tim-toady

For what it's worth, here's an example of a Backbone view that's using delegation and a single event listener as a callback for all of the individual blocks in the charts: http://blog.documentcloud.org/blog/2011/10/entity-charts/

To be fair, Backbone's events hash idiom is implemented using event delegation straight out of the box. It's not forgotten at all.

Although to your point: since Backbone offers no OOTB mechanism for sub-views, it offers no OOTB support for event delegation on a parent view. I just wanted to clarify where that line is drawn wrt event delegation being "forgotten".

Yes, I should have been more clear on that. I mentioned that because SC says that they may have a view (DOM element) that contains a single button (or whatever). This means they bind events on each one of those buttons, even if they have 100 of those at any given time on the DOM. Maybe they have some other form of event delegation but they haven't mentioned it.

I'd must rather see these kinds of posts after a big rewrite has proven the new technologies were the right choice!

The main reason is quite obviously for feedback. SoundCloud is a community-driven site, and we want to get really early feedback about features, design, etc. Another part of the feedback is exactly what's happening here with sharing our techniques and seeing the results. Hopefully the outcome of this blog post is that some other people will learn something, but also that some people will point out things so that we ourselves can learn.

> there are many bugs, most features are not implemented,

We're definitely aware of the features not yet implemented, but if you find bugs (or are really missing a particular feature), please do use the feedback form to let us know!

Cheers, Nick

I think the new design and architecture is coming out great and I don't mean to discourage experience sharing. If anything, better way to have said would be:

I hope that you will post a few follow-ups to this as you get closer to release what/if anything has changed in your stack, approach, and gotchas found building this complex of a single page/backbone app.

Thanks!

It's a little bit like this anti-pattern.

Jokes aside, I wonder how on-going development and maintenance is for a "single file" website...

It was definitely something we thought about, and even discussed with the devs from Twitter. Twitter has a very different use-case to SoundCloud. When you follow a link to Twitter, it's usually to read a single tweet (or maybe a handful), and that's it. SoundCloud is visited by someone who is already willing to invest at least a couple of minutes to listen to a tune, and is much more likely to explore the site. Therefore, the value of making further navigation of the site fast (via client-side rendering, etc) is weighted differently at SoundCloud than at Twitter.

Do anyone knows any pattern to have the server templates sent to backbone avoiding duplication?

  Templates={}
  Templates['templatename']=function(){/*compiled template*/}

I've been using the desktop client exclusively because the website is often so painful on my 2008 macbook, but it only shows new tracks, not all the other interactions that show up on the dashboard, which means I'm missing out on a lot of good tunes.

(You probably knew that but I thought it should be pointed out.)

You can combine these with RequireJS as well. Instead of:

  define(['a', 'b', 'c'], function () {
    var a = require('a');
    var b = require('b');
    var c = require('c');
    ...
  });

  define(['a', 'b', 'c'], function (a, b, c) {
    ...
  });

  define(function(require) {
     var a = require('a');
     var b = require('b');
     var c = require('c');
     ...
  });

- Boilerplate is greatly reduced (though still present) - Way less error-prone since you're not relying on keeping two separate lists of dependencies in same the order

But, it still does require rewriting before use (to add the module name), so I don't see a huge win here either way.

I'll also point out that this "sugared" syntax was added to requirejs after we started developing. If it were there at the start, perhaps we would have used that instead.

    Wikipedia                               Gmail
       <------------------------------------->
    Traditional                              SPA

Google Maps is probably a much better example.

The time I finish the app, I will tweak and optimize loading either by AJAX or implement something like backbone views.

Now we're building a mobile version, and having built the API in the first phase, we've got enough to go on to do it all via Backbone.

Additionally, when developing for mobile you're much more aware of bandwidth restrictions, so the ability to load only what you need becomes useful. When you're flicking through a bunch of pages that use the same view but with different data, an SPA lets you load only what you need.

Is there any data on how much SoundCloud's transition to a single-page interface decreased latency during navigation relative to the traditional page-loading model?

Apologies if these questions have obvious answers. I tried to sign up for the beta but the party was full, and I'm not familiar with SoundCloud's interface.

For IE9: some. Backbone automatically detects pushState availability and fallsback to a hashbang system allowing the SPA to work.

For IE <= 8: none.

> Is there any data on how much SoundCloud's transition to a single-page interface decreased latency during navigation relative to the traditional page-loading model?

Not yet, but that would definitely be a metric we'll be collecting. We're still working very hard on increasing the performance, so it'd be a moving value right now.

> I tried to sign up for the beta but the party was full

No worries -- you're in the queue and we're gradually expanding the rollout, so you'll get an email soon. For everyone else, you can join the beta by signing in at http://next.soundcloud.com

Can I propose a corrolary to Greenspun's Tenth Rule?

"Any sufficiently complicated Backbone program contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Ember.js"

"Inside of every Ember.js application is a leaner, meaner, far faster, built-with-less-headaches Backbone.js app trying to get out."

I'm not sure if "insertion of subviews" only happens once or on every render()... ideally only the subviews have to be rerendered - not the parent view which is "heavy".

Views state exactly which attributes on their model should trigger the rerender when they change, and no others. If you have a very high level view which has a sizeable tree of subviews underneath it, then its subviews will probably be the ones actually displaying data and that it will essentially just be a 'composite' view and will never rerender.

Views which bind to collections (eg: Lists) have special logic for adding and removing subviews without rerendering all of them.

i found javascripts lack of weak references extremely problematic when trying to develop a larger backbone app

[1]: http://stackoverflow.com/questions/7379263/disposing-of-view...

https://github.com/thoughtbot/backbone-support

I haven't dug into how it's done, but I feel like JavaScript apps are harder to test and verify. It's not like running unit tests on your server code. To truly verify you need to test the entire application in each supported browser.

http://wiki.ecmascript.org/doku.php?id=harmony:weak_maps

Do you have any benchmarks of Next SoundCloud's performance compared to the existing SoundCloud?

In the places where we can control the performance, we do that very carefully: CDN loading of all assets, intelligent caching techniques, and of course, finding and removing bottlenecks in the code.

@jarcoal, would you mind letting me know some of your details which might affect performance (which country you're in, what browser, what speed is your computer)? Email me directly at fisher at soundcloud if you'd prefer not to share here. Thanks.

I don't see webengage.com or a link to it anywhere on this link. Did you post on the wrong link by chance?

edit: There are also no arrows and the text 'webengage' doesn't appear in the blogpost page source...