Thursday, 2 April 2009

ActiveRecord::Validations in ActiveResource

The holy grail for ActiveResource users is for ARes to actually behave like ActiveRecord. In theory, ARes is just like AR, but in practice it's only kinda, sorta like AR... but missing a few bits that really seem to make all the difference.

ARes is still missing fundamental functionality that we have all grown to know and love... It all looks alright on the surface, but you can't help but notice the giant glowing absence the moment you decide to hide your models away in a Web service and then try to use ARes to implement a Railsy front-end.

Needed functionality includes:

  • Associations (ie has_many/belongs_to)
  • the usual suspects of callbacks (eg before_save)
  • safe-making your attributes (eg attr_accessible)
  • Widget.count
  • Actual conditions in finders (eg :conditions => {:name => 'Joe Bloggs'}
  • and the all-important Validations

I need my validations. The funky way rails handles AR errors is one of the things that makes Rails so special. I love to be able to just type validates_presence_of :foo and for everything else to Just Work.

ARes doesn't bother with them at all - and in that case I hardly see why Rails can call it AR-like when these are missing. Oh yes, sure, you can overload the validate method on your model object, but that seems very crude! Like having to hand-write your database connection code for each model. :P

All I can say is why can't I have validates_presence_of independently to the database connection? It's not really necessary - so why are Validations still locked inside the db-wrapper?

In my opinion, ActiveResource needs a lot of upgrading. Unfortunately, that looks like a fair bit of work... and we don't know how long that will take, and whether it will just be superceded once Merb merges with Rails.

Luckily we have an interim solution, in the form of a plugin called HyperactiveResource. It is fairly crude, but it seems to roughly give us an ActiveRecord-like interface that works fairly well.

Before I hit the code, the plugin already came with a lot of the currently-missing functions - rebuilt with ARes-style processing. They also had a rough implementation of Associations (not entirely AR-like, but getting there). I've been working on adding validations and validation-callbacks.

I can't say it works perfectly as I've just started working on it, as of this morning; but I've already got the basic validations working without falling over completely and I'm using the models auto-generated by restful-authentication to test it.

It's a start...

2 comments:

Matt Gordon said...

I'm right there with you on wishing that Ares was more like AR. I checked out your fork of hyperactive resource on Github and was happy to see that someone was maintaining/improving it.

Unfortunately, you've copyrighted your changes. If you really want to see this kind of functionality in Rails, you should keep the code free. It may still be "open source" in the sense that I can see your changes, but I can't make changes or use it in any of my projects.

Please consider opening your changes up and starting a community effort to get Ares where it needs to be.

Taryn said...

Hi Matt - sadly I'm working on this on company time and they want their name on it. It's their call...
As it is - the code is available to anyone to make derivatives.
I'm not really certain of the legal implications of using that in rails... but I'm happy to hear suggestions as to how to go forward.