Rails rendering json partial in model

Question

In our rails 3.2 app, we are using Jbuilder to render our json responses (nothing special here). The json view could be as simple as this:

_model_name.json.jbuilder

json.extract!(page, :id, :name, :url_name)

We often need to return a deeply nested json object, and Jbuilder partials work great for this:

_page.json.jbuilder

json.extract!(page, :id, :name, :url_name)
json.page_images (page_images) do |json, page_image|
    json.partial! page_image
end

The last example will retrieve the page, and nested page_images, json representation... again nothing special.

Often, a single partial will call another, and may return a nested json object 2 or 3 levels deep.

PROBLEM

Like I mentioned above, we use Jbuilder partials to quickly link multiple partials together to form a deeply nested json object for the view. We also need build these exact same nested objects as a hash (rather than json) AND make them available to a model.

It's simple to get a Jbuilder object to output a hash using the .attributes! method, but we're having some serious difficultes giving Jbuilder access to the view partials from a model.

Looking at the Jbuilder source, it looks like the JbuilderTemplate class needs access to the controller context to make everything work.

We might try something like this:

class SomeClass

  def initialize pages
    @pages = pages
    @context = ActionController::Base.new
  end

  def to_hash
     builder = JbuilderTemplate.new(@context)
     builder.pages(@pages) do |json, page|
        json.partial! page
     end
     builder.attributes!
  end
end

The example above is obviously incorrect, but it illustrates what needs to be done. I'm just not sure how to pass initialize a controller from a model, and then pass the controller context.

Some leads that we are following:

Can anyone help point us in the right direction?

Jimmy Lien · Accepted Answer · 2016-06-22 20:05:24Z

2

I'm pretty sure you were on the right track here. You should be able to call json.array! and build the partial normally if you pass the block directly in the initializer.

def to_hash
  builder = JbuilderTemplate.new(@context) do |json|
    json.array! @pages, partial: 'path/to/partial'
  end
  builder.attributes!
end

answered Jun 22, 2016 at 20:05

Jimmy Lien

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Erik Lott · Accepted Answer · 2012-02-11 12:03:55Z

1

Couldn't find a solution. We fell back to using as_json to configure our model json output.

answered Feb 11, 2012 at 12:03

Erik Lott

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1 Comment

Jimmy Lien Over a year ago

Have a look at my answer below if you still want to be able to reuse your jbuilder templates.

Mark Swardstrom · Accepted Answer · 2013-06-21 17:27:07Z

0

I use ActiveModel::Serializer to do this exact same thing. You can render the json in the model or whereever - we do this to pre-populate the cache.

The syntax for doing this wasn't initially obvious, so I'm posting here:

ItemSerializer.new(item).to_json

answered Jun 21, 2013 at 17:27

Mark Swardstrom

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Comments

sandrew · Accepted Answer · 2014-01-15 16:48:38Z

0

If you really need this functionality, I can show you some shim:

c = ActionController::Base.new
c.instance_variable_set '@item', Item.find(5)
JSON.parse c.render_to_string('items/show')

answered Jan 15, 2014 at 16:48

sandrew

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