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POHow to build a JSON response made up of multiple models in Rails
 

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  1. POHow to build a JSON response made up of multiple models in Rails
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    <h2>First, the desired result</h2> <p>I have <code>User</code> and <code>Item</code> models. I'd like to build a JSON response that looks like this:</p> <pre><code>{ "user": {"username":"Bob!","foo":"whatever","bar":"hello!"}, "items": [ {"id":1, "name":"one", "zim":"planet", "gir":"earth"}, {"id":2, "name":"two", "zim":"planet", "gir":"mars"} ] } </code></pre> <p>However, my <code>User</code> and <code>Item</code> model have more attributes than just those. I found a way to get this to work, but <strong>beware</strong>, it's not pretty... Please help...</p> <h3>Update</h3> <p>The next section contains the original question. The last section shows the new solution.</p> <hr> <h2>My hacks</h2> <h3>home_controller.rb</h3> <pre><code>class HomeController &lt; ApplicationController def observe respond_to do |format| format.js { render :json =&gt; Observation.new(current_user, @items).to_json } end end end </code></pre> <h3>observation.rb</h3> <pre><code># NOTE: this is not a subclass of ActiveRecord::Base # this class just serves as a container to aggregate all "observable" objects class Observation attr_accessor :user, :items def initialize(user, items) self.user = user self.items = items end # The JSON needs to be decoded before it's sent to the `to_json` method in the home_controller otherwise the JSON will be escaped... # What a mess! def to_json { :user =&gt; ActiveSupport::JSON.decode(user.to_json(:only =&gt; :username, :methods =&gt; [:foo, :bar])), :items =&gt; ActiveSupport::JSON.decode(auctions.to_json(:only =&gt; [:id, :name], :methods =&gt; [:zim, :gir])) } end end </code></pre> <hr> <h1>Look Ma! No more hacks!</h1> <h2>Override <code>as_json</code> instead</h2> <p>The <a href="http://api.rubyonrails.org/classes/ActiveRecord/Serialization.html#M001874" rel="nofollow noreferrer">ActiveRecord::Serialization#as_json</a> docs are pretty sparse. Here's the brief: </p> <pre><code>as_json(options = nil) [show source] </code></pre> <p>For more information on <code>to_json</code> vs <code>as_json</code>, see the accepted answer for <a href="https://stackoverflow.com/questions/2572284/override-to-json-in-rails-2-3-5">Overriding to_json in Rails 2.3.5</a></p> <h2>The code sans hacks</h2> <h3>user.rb</h3> <pre><code>class User &lt; ActiveRecord::Base def as_json(options) options = { :only =&gt; [:username], :methods =&gt; [:foo, :bar] }.merge(options) super(options) end end </code></pre> <h3>item.rb</h3> <pre><code>class Item &lt; ActiveRecord::Base def as_json(options) options = { :only =&gt; [:id, name], :methods =&gt; [:zim, :gir] }.merge(options) super(options) end end </code></pre> <h3>home_controller.rb</h3> <pre><code>class HomeController &lt; ApplicationController def observe @items = Items.find(...) respond_to do |format| format.js do render :json =&gt; { :user =&gt; current_user || {}, :items =&gt; @items } end end end end </code></pre>
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