Previously, I’d been using something like

respond_to do |format|
  format.js { render :json => @record.to_json(:methods => [:foo, :bar]) }
end

But obviously, this is no longer DRY in Rails 3. So I cleaned that up to work with the new responders:

respond_to :html, :json

def show
  respond_with @record
end

But that left me with a problem: where to put the :methods? From the documentation I couldn’t really figure this out all that well, which is why I’m posting this. The release notes for Rails 2.3.3 let me know that there’s now an as_json, which I knew, but turns out it works a bit different than I thought I’d understood from the docs. It should basically just deliver a hash, which will be converted to JSON by Rails. So add something like this to your model:

def as_json(options = {})
  attributes.merge({:foo => foo,
                    :bar => bar
                   })
end

And you’ll be all set again.