Question

I am converting a User object to json via:

user.to_json :methods => :new_cookies

the new_cookies method is:

cookies.all :include => :fortune, :conditions => {:opened => false}

This embed the cookies inside the user json object, but I want fortune to be embedded inside the cookie object as well. I passed inside :include => :fortune but that doesn’t that work.

Is this possible?

Models:

class User < ActiveRecord::Base
    has_many :cookies
    has_many :fortunes, :through => :cookies

    def new_cookies
        cookies.all :include => :fortune, :conditions => {:opened => false}
    end
end

class Cookie < ActiveRecord::Base
    belongs_to :user
    belongs_to :fortune
end

class Fortune < ActiveRecord::Base
    serialize :rstatuses
    serialize :genders 

    has_many :cookies
    has_many :users, :through => :cookies
end

Answer 1

I am not sure that the :includes => :fortune option works as you expect (or perhaps at all) — near the end of this section of the current Rails guides it mentions this option for finder methods other than .all.

I assume it works similarly to the new Active Relation query interface, e.g. Cookies.include(:fortunes).where(:opened => false) — in this case, Rails “eager loads” the related records, meaning fortunes are fetched as part of the query for cookies. This is a performance enhancement, but doesn’t otherwise change the behavior of Rails.

As I noted in the comments, I think as_json will do what you want — it defines what is and is not part of the object when serialized using to_json. You specify methods that should be called in addition to (or to exclude) the methods of the data-backed object itself, for example, your new_cookies method.

In this example, I have added as_json to User (which gets Cookie) and also to Cookie in hopes that each cookie will nest its fortunes in its JSON. See below for an alternative.

class User < ActiveRecord::Base
  has_many :cookies
  has_many :fortunes, :through => :cookies

  def as_json(option = {})
    super(:methods => :new_cookies)
  end

  def new_cookies
    cookies.all :conditions => {:opened => false}
  end
end

class Cookie < ActiveRecord::Base
  belongs_to :user
  belongs_to :fortune

  def as_json(options = {})
    super(:methods => :cookie_fortune)  # or perhaps just :fortune 
  end

  def cookie_fortune
    self.fortune
  end
end

In a case where I was writing an API and didn’t need to reflect the nested relationships between objects in the JSON, in the controller, I used something like

respond_to do |format|
  format.html 
  format.json { render json: { :foo => @foo, :bar => @bar }}
end

to produce parallel nodes (objects) in the JSON.