ActiveModelSerializer with Sinatra

Question

Can I use active_model_serializers with Sinatra? If not, is there any better way for json output in Sinatra for building a web service?

Awesome. I'm still not sure if I made a right choice using Sinatra for web service (I'm writing backend of my application as a service), but we'll see. — Bhushan Lodha, Nov 07 '14 at 09:02
well why not, if you start having 50+ end points, might be more difficult to organize in sinatra but... why not — apneadiving, Nov 07 '14 at 09:11
@apneadiving - I think Sinatra is the way to go. I created an API with 60 endpoints. It is easy to organize. — B Seven, Nov 08 '14 at 14:46
@BSeven well you know Rails provides much security for free, taste and colours :) — apneadiving, Nov 08 '14 at 15:25

score 1 · Answer 1 · answered Nov 07 '14 at 09:29

Yes, you can. However, the design and architecture of AMS is strongly focuses on ActiveModel instances, therefore if you don't use an ActiveModel-based library (such as Mongoid, ActiveRecord, etc) the choice may be overkill.

Still, the approach reflects the common Presenter pattern applied to JSON serialization. You can easily create your own simple library to extract the attributes you define from an object you pass.

Sinatra also provides some JSON serialization extensions. What they do by default, is to call as_json. That's not the best approach, it is not extremely flexible, but you can combine those two elements to create your own solution, or start from scratch.

I'll be using ActiveRecord – Bhushan Lodha Nov 07 '14 at 09:31 — Bhushan Lodha, Nov 07 '14 at 09:31

score 1 · Answer 2 · answered Jan 22 '15 at 17:37

You can, includes a json.rb inside the lib folder with the following piece of code and do require this file on your application.rb .

# lib/json.rb

module Sinatra
  module JSON
    def json(object, options={})
      serializer = ActiveModel::Serializer.serializer_for(object, options)
      if serializer
        serializer.new(object, options).to_json
      else
        object.to_json(options)
      end
    end
  end
end

To use just do

get '/foo' do
  json Foo.find(params[:id])
end

get '/bar' do
  json Bar.find(params[:id]), { scope: self }
end

I did this gem to help: https://rubygems.org/gems/sinatra-active-model-serializers — Saulo Santiago, Feb 10 '15 at 17:55

score 0 · Answer 3 · answered Nov 08 '14 at 15:04

I used to_json to return JSON output from Sinatra API's. It turns out that there are dozens of JSON gems for Ruby, of varying efficiency.

One approach is to create list of attributes for each object that you want to render to JSON. For example, if your User has an image that you don't want to render, you could create a blacklist for the User class:

JSON_BLACKLIST = [ 'image' ]

Then, when you render the JSON, you can call:

user.attributes.reject{|a| JSON_BLACKLIST.include?( a )}.to_json

ActiveModelSerializer with Sinatra

3 Answers3