render :json does not accept options

Question

I'd love to use render :json but it seems its not as flexible. Whats the right way to do this?

respond_to do |format|
  format.html # index.html.erb
  format.xml  { render :xml => @things }

  #This is great
  format.json { render :text => @things.to_json(:include => :photos) }

  #This doesn't include photos
  format.json { render :json => @things, :include => :photos }
end

Answer 1

I've done something similar with render :json. This is what worked for me:

respond_to do |format|
    format.html # index.html.erb
    format.json  { render :json => @things.to_json(:include => { :photos => { :only => [:id, :url] } }) }
end

Answer 2

I guess this article can be useful for you - Rails to_json or as_json? by Jonathan Julian.

The main thought is that you should avoid using to_json in controllers. It is much more flexible to define as_json method in your model.

For instance:

In your Thing model

def as_json(options={})
  super(:include => :photos)
end

And then you can write in your controller just

render :json => @things

Answer 3

Managing complex hashes in your controllers gets ugly fast.

With Rails 3, you can use ActiveModel::Serializer. See http://api.rubyonrails.org/classes/ActiveModel/Serialization.html

If you're doing anything non-trivial, see https://github.com/rails-api/active_model_serializers. I recommend creating separate serializer classes to avoid cluttering your models and make tests easier.

class ThingSerializer < ActiveModel::Serializer
  has_many :photos
  attributes :name, :whatever
end

# ThingsController
def index
  render :json => @things
end

# test it out
thing = Thing.new :name => "bob"
ThingSerializer.new(thing, nil).to_json