[dojo-contributors] Dojo 1.9 Proposal

Kenneth G. Franqueiro kgf at dojotoolkit.org
Tue Oct 16 12:08:47 EDT 2012

Further responses inline.

On 10/16/2012 11:52 AM, Kitson Kelly wrote:
> Comments inline...
> On 16 October 2012 16:10, Kenneth G. Franqueiro <kgf at dojotoolkit.org
> <mailto:kgf at dojotoolkit.org>> wrote:
>     As with the last time the idea of web storage + dojo/store was brought
>     up, I would raise concern at the idea of introducing this "feature".  I
>     may not have the most informed of opinions on the matter, but the
>     following things stick out to me:
>     * Which way would we "solve" this?  One write per atomic store
>     operation, or have developers call a method to persist all items at
>     once?  (Based on your idea of using Cache, I'm guesing the former; I'm
>     inclined to expect that the latter may actually perform better - i.e.
>     write all data to one key at once.)
> The "why" to me is that we provide a Memory store with a consistent API
> interface, but if you want to use Web Storage, you have to learn another
> API.  None of the widgets and other objects which are "data aware" can
> leverage Web Storage, without some level of bespoke code.  I personally
> think this is making it difficult for creation of "offline" capable
> applications with Dojo/Dijit both in the desktop and mobile space.

It's not difficult to extend dojo/store/Memory with localStorage support
if you want it.  We do it (though perhaps not ideally, going back to the
points in my previous reply) in one of the simple dgrid demos.

> Of course an end developer could directly use the HTML5 Web Storage.  I
> maybe missing something, but if you needed to develop an application
> that persisted date between page loads without always having a
> connection to a server, outside of using cookies, how would you
> accomplish this with Dojo?

Let me pose an unrelated but equivalent question, in an attempt to
illustrate a point: how would you iterate the keys of an object with
Dojo?  The answer is, you wouldn't.  Dojo doesn't make a habit of
providing solutions for problems that are already solved.

>     * But moreover, who's to say we really have the right to prescribe one
>     or the other for every situation, when in reality it would take someone
>     very few lines of code to implement either approach him/herself?
> Again, how would you connect a Dijit, dgrid, GridX and any other
> dojo/store API to Web Storage?

You would write a few lines of code to extend dojo/store/Memory in
whichever way you see fit to back it with localStorage.  Again, I think
it's disingenuous for us to make the decision as to "whichever way" for
devs.  It seems more like grounds for a tutorial (exploring multiple
solutions) than a feature.

>     * Performance implications (see perhaps
>     http://www.nczonline.net/blog/2012/04/25/the-performance-of-localstorage-revisited/
>     and in particular, the first link in the footnotes)
> A valid end-developer concern about which approach to take.  I don't
> think performance should preclude us from considering it though.  Also,
> as some of the comments have made, read into memory, work on data set,
> save back to storage.  Unless I am missing something though, I don't see
> a way to easily persist data between sessions to create offline capable
> applications any other way.

I just don't want to see us implement something that encourages or makes
it easy for people to shoot themselves in the foot.  My point of linking
that article wasn't so much about localStorage vs. something else, as it
was cautioning against leaning heavily on it (and perhaps in the wrong way).

>     * Now you're also raising the implication of affecting another API
>     (dojo/store/Cache) just for the sake of a single implementation, which
>     to me sounds suspect (let alone that the potential implementation in
>     question also sounds suspect to begin with).  I'm also not really sure I
>     understand what kind of changes you have in mind.
> Possibly.  That is why it is a proposal and the benefits of discussing
> in the open. :-)
> If we affect the Cache API in a way that break compatibility, then
> obviously that is a non starter, but I would suspect people maybe
> re-inventing the wheel, in that I have a level of concern with
> dojo/store/Cache that it has no real logic of what data gets persisted
> where other than "avoid fetching the same data again".  It simply copies
> all fetched data to both stores and if it doesn't think it has changed
> retrieves it from the cached store.  Whenever anything is .put() it
> is immediately propagated to both stores.  While Cache might not be the
> right place to add it, there almost needs to be a mediation layer that
> can be used to track transactions and commit those to a remote store in
> a configurable fashion as well as synchronise between a local and remote
> store in a configurable way.  So I don't wholly see it as a
> single implementation argument.  I see it as a dojo/store compatible API
> for Web Storage and providing an intelligent mechanism to
> replicate/synchronise data between data stores.

This sounds like it's sorely overcomplicating the scenario as opposed to
what Cache currently solves.  It sounds to me like it should be a
separate entity, if it is to exist at all.

> If it ends up being a "bad idea" there is plenty of time between now and
> the release of 1.9 to agree to not do it, but if there is a "this might
> work" then I am willing to expend time and effort on it.
> Again, the main use case would be to allow the creation of offline
> capable applications that will function between page re-loads or across
> pages.
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