[LRUG] Encapsulation/Responsibility delegation and API versioning.

[Ian Leitch]

Hey list,

I'm working on a Rails API that's the backend for an iPhone app. Given
that I'll have no control over when a user maybe choose to up upgrade
to the latest version of the app, I'm taking steps to ensure that each
of my API versions are very much self-contained. When I need to bump
the version, i'll simply duplicate the controllers.

I've worked on apps before where you'd have multiple controller
versions calling down to a shared model method - this is a time bomb I
want to avoid.

The smell that's now beginning to emerge is that controllers are
getting fat with protected helper methods that build data structures
for conversion into JSON. Normally I'd push these down into the
model/some class, but like I said, I need API versions to remain
self-contained.

My initial thought was to suffix model methods with the API version,
i.e attributes_for_json_api_v1 but that'll soon result in fat models,
which I dont want.

What solutions have other people used for this problem?

I'm almost considering a layer in between my controllers and models,
almost like a presentation layer from model to controller. Mixins
could help here... perhaps something like this?
https://gist.github.com/1162618
Could get messy if the controller uses a large number of models?
Thoughts welcome!

Cheers
Ian