Rails tip #5: Atom param parser
The Atom Publishing Protocol is wonderfully RESTful, so it's a natural fit for a Rails application.
One thing you'll run into, though, is that AtomPub posts application/atom+xml data rather than the usual application/x-www-form-urlencoded stuff, so you'll have to write some extra code to handle it.
The good news is that ActionController::Base helps you out. Instead of having to branch on the request type and fatten your controller, you can register a custom param_parser.
So, we wrote Hash.from_atom to transform the incoming xml into the usual { :entry => { ... } } params. Then, we registered it in an initializer:
ActionController::Base.param_parsers[Mime::ATOM] = lambda do |body|
Hash.from_atom(body)
end
And our controller can now handle either regular form postings or AtomPub entries with the same line of code:
class EntriesController < ApplicationController
def create
@entry = @collection.entries.build(params[:entry])
# ...
end
end
Not bad.
5 Rails tips
Each day this week, Joachim and I will post something we've learned in our time programming together. It's fun to do, and we might just win something as well.
So far, we've written: