How do I expose data in a JSON format through a web service using Rails?

Question

Is there an easy way to return data to web service clients in JSON using Rails?

Answer 1

Rails resource gives a RESTful interface for your model. Let's see.

Model

class Contact < ActiveRecord::Base
  ...
end

Routes

map.resources :contacts

Controller

class ContactsController < ApplicationController
  ...
  def show
    @contact = Contact.find(params[:id]

    respond_to do |format|
      format.html 
      format.xml {render :xml => @contact}
      format.js  {render :json => @contact.json}
    end
  end
  ...
end

So this gives you an API interfaces without the need to define special methods to get the type of respond required

Eg.

/contacts/1 # Responds with regular html page

/contacts/1.xml # Responds with xml output of Contact.find(1) and its attributes

/contacts/1.js # Responds with json output of Contact.find(1) and its attributes

Answer 2

http://wiki.rubyonrails.org/rails/pages/HowtoGenerateJSON

Answer 3

Rails monkeypatches most things you'd care about to have a #to_json method.

Off the top of my head, you can do it for hashes, arrays, and ActiveRecord objects, which should cover about 95% of the use cases you might want. If you have your own custom objects, it's trivial to write your own to_json method for them, which can just jam data into a hash and then return the jsonized hash.

Answer 4

There is a plugin that does just this, http://blog.labnotes.org/2007/12/11/json_request-handling-json-request-in-rails-20/

And from what I understand this functionality is already in Rails. But go see that blog post, there are code examples and explanations.

Answer 5

ActiveRecord also provides methods to interact with JSON. To create JSON out of an AR object, just call object.to_json. TO create an AR object out of JSON you should be able to create a new AR object and then call object.from_json.. as far as I understood, but this did not work for me.