[Catalyst] Dispatching with Chained vs HTTP method

Toby Corkindale tjc at wintrmute.net
Wed May 7 02:05:21 BST 2008

On Thu, May 01, 2008 at 08:41:26AM +0200, Zbigniew Lukasiak wrote:
> On Thu, May 1, 2008 at 6:23 AM, Toby Corkindale <tjc at wintrmute.net> wrote:
> > On Wed, Apr 30, 2008 at 11:24:36AM +0200, Zbigniew Lukasiak wrote:
> >  > Hi Toby,
> >  >
> >  > I don't know if you are aware - but building a REST-like CRUD
> >  > interface to DBIx::Schema is my long term goal (started with
> >  > Catalyst::Example::InstantCRUD).  Do you think we could collaborate?
> >
> >  Sure, if you liked.
> >
> >  I'm not sure I want to aim for total DBIx::Class:Schema emulation, as I
> >  think there are many corner cases which could start getting hard to
> >  implement /well/.
> >
> >  I'd rather approach creating something which does a sub-set of the
> >  features, but does them well. For instance, how would you handle
> >  transactions? Or
> My understanding is that you can nest transactions in DBIC - so my
> plan is just add a transaction wherever I think it is needed.

Ah, I was thinking of transactions vs a REST API, eg:
    PUT /user/1234/account_balance?subtract=1
    POST /user/4567/account_balance?add=1
Since those are two separate HTTP requests, and REST specifically states you
cannot maintain state on the server, how would you perform those two
operations inside a transaction?

(My "solution" is to implement it in one request, like:
    PUT /user/1234/money_transfer?user=4567;amount=1
However that is not CRUD-like, nor a direct mapping of DBIC functionality to

> >  specifying complex searches with aggregate clauses and self-joins? Those
> >  would seem to be more suited to an RPC protocol rather than an
> >  object-based REST situation. I think?
> I admit that my main goal is mostly a kind of browser-REST (but with
> the option for 'real' REST) - so I start with HTML forms (for now I
> discovered Rose::HTML::Form - and I like it) that would define the
> available searches.  I guess this might look restricting for you.  By
> the way have you seen my Advent article:
> http://catalyst.perl.org/calendar/2007/16 ?

Oh, right.
I'm definitely making a 'real' REST interface; I'm basing it around a DBIC
Schema for the moment, but I'm not attempting to provide 100% of the DBIC
features via REST; I figure if you want that, you can just use a real DB
Instead I'm trying to provide a simple set of basic REST calls, and a framework
for dealing with foreign keys, and then allow extensions on top of that for
things such as the example above where you can't use simple calls.

I think it sounds like we're really working towards fairly different goals at
the moment.
Whereas you're looking at using forms and validation there, I'm more interested
in having a DB which provides the validation via constraints and stored
procedures, and using Catalyst as a fairly thin layer to access it and provide
extensions via the DBIC-SChema class.

The REST API has proven quite cute when used against a quickly hacked-up pure
javascript web UI though; it's blindingly fast compared to having pages built
and served and rendered!


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