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POEager-loading in Rails 3.1 controller action which responds_to json
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copied!<p>Here's what I have so far:</p> <pre><code>class Show < ActiveRecord::Base belongs_to :event # use default_scope so shows are ordered by date by default default_scope order("date ASC") end class Event < ActiveRecord::Base has_many :shows, :dependent => :destroy has_and_belongs_to_many :users scope :future, lambda { includes(:shows).joins(:shows).where("shows.date > ?", Date.today).group("event_id") } def start_date shows.first.date end def end_date shows.last.date end def ends_in_future? end_date > Date.today end end </code></pre> <p>I would like to create a controller action to use with jqGrid. So far using <code>Event.includes(:shows).all.to_a</code> returns all the shows in the JSON string, but I can't get hold of <code>start_date</code> and <code>end_date</code>, which is kinda understandable. Is it possible to have derived/calculated properties rendered in JSON? </p> <p>I also notice the shows for each event are not in the JSON string. Is there any way I can get all the events, complete with child shows entities, rendered in the JSON string?</p> <p>Many thanks, Dany.</p> <p>EDIT: Partially solved this by using <code>as_json(:include => :shows)</code> in the controller action. This returns the event and all the associated shows for each event. The only thing remaining is to figure out how I can include <code>start_date</code> and <code>end_date</code> in the json string...</p> <p>EDIT: Here was my original controller action code - it may not be the best code since I'm still feeling my way around Rails:</p> <pre><code>matches = Event.includes(:shows).all respond_to do |format| format.json {render :json => matches.as_json(:include => :shows)} end </code></pre> <p>As it turned out I don't have to run the query first - it can just be part of responding to the json request. I should've read the as_json specs a lot closer first! Here's the solution in my controller action:</p> <pre><code>respond_to do |format| format.json {render :json => Event.all.as_json(:include => :shows, :methods => [:start_date, :end_date])} end </code></pre> <p>That renders everything, including the "derived" method. Unfortunately that seems to generate a lot of queries. This provides the json string I want, but is it the best way? Would love to hear any improved methods.</p>

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