Rails 4 - How to render JSON regardless of requested format?

Question

I'd like a Rails controller (all of them, actually, it's an API) to render JSON always always.

I don't want Rails to return "route not found", or try and fail to find an HTML template, or return 406. I just want it to automatically and always render JSON, e.g. from a RABL or JBuilder view.

Is this possible? Related questions seem to have answers that have the aforementioned downsides.

Chesna

Answer 1

You can add a before_filter in your controller to set the request format to json:

# app/controllers/foos_controller.rb

before_action :set_default_response_format

protected

def set_default_response_format
  request.format = :json
end

This will set all response format to json. If you want to allow other formats, you could check for the presence of format parameter when setting request.format, for e.g:

def set_default_response_format
  request.format = :json unless params[:format]
end

Quick

Naturally, this can be placed in /app/controllers/application_controller.rb to have an application-wide effect (strictly if your app is an API) – Dobbins

FWIW, I just tried this solution in Rails 5 (with html format, vs json) and Rails wouldn't take :html, it needed 'html' as a string. Not sure why it wouldn't accept a symbol for request.format, but once I changed it to 'html' from :html it worked great. – Carbohydrate

in rails 5 I use request.format = :json unless request.format.symbol – Rustproof

or inline it: ``` before_action { request.format = :json unless request.format } ``` – Gouge

Answer 2

You can use format.any:

def action
  respond_to do |format|
    format.any { render json: your_json, content_type: 'application/json' }
  end
end

Permafrost

Answer 3

It's just:

render formats: :json

Donnelldonnelly

@Akaisteph7 Not quite sure what you mean. This answer is clearly different from other. – Donnelldonnelly

What I mean is that you should add some context to your answer. – Antagonize

Answer 4

I had similar issue but with '.js' extension. To solve I did the following in the view: <%= params.except!(:format) %> <%= will_paginate @posts %>

Sihunn

Answer 5

I tried the above solutions and it didn't solve my use case. In some of the controllers of my Rails 4.2 app, there was no explicit render called. For example, a service object was called and nothing was returned. Since they are json api controllers, rails was complaining with a missing template error. To resolve I added this to our base controller.

  def render(*args)
    options = args.first
    options.present? ? super : super(json: {}, status: :ok)
  end

It's a large app I'm converting to Rails 5, so this is just a safety measure as I removed the RocketPants gem that seemed to do this automatically.

As a note, my controllers inherit from ActionController::Base

Electroballistics

Answer 6

I usually put it like this and it works. The lambda symbol ( => ) near :json is important.

def greet_action
  msg = {:greet => "hello"}
  render :json => msg
end

Tamtama

Answer 7

Of course:

before_filter :always_json

protected

def always_json
  params[:format] = "json"
end

You should probably put this in a root controller for your API.

Outspan