| Scrawlon

The following is a quick guide to the FatSecret OmniAuth gem. With this gem, you can obtain authorization to access a user’s FatSecret account. You’ll use your FatSecret API consumer_key and consumer_secret to work with the example app. If you’re not familiar with OmniAuth, you might want to browse the README.

Install a dummy User app

Before we do anything, we need a Rails app with a User model. We’ll take advantage of the Rails Composer project to get us started.

First let’s clone the bare dummy app:
git clone https://github.com/RailsApps/rails3-devise-rspec-cucumber.git
Now let’s initialize and start the app to make sure everything is working:
cd rails3-devise-rspec-cucumber bundle install
rake db:migrate
rails s
Open ‘http://localhost:3000’ in your internet browser. You should see a simple web page with ‘login’ and ‘Sign up’ links at the top.

Install FatSecret OmniAuth

If you followed the instructions to set up the example Rails app, return to your command prompt and stop the Rails server with ctrl-c.

Add FatSecret OmniAuth gem to your Gemfile: gem 'fatsecret-omniauth'
Install the gem: bundle install
Create omniauth.rb in the config/initializers directory, and add the following code with your real FatSecret key and secret:

Rails.application.config.middleware.use OmniAuth::Builder do
  provider :fatsecret, 'consumer_key', 'consumer_secret'
end

Create an api_token model/controller

Generate the model and migrate the database. This gives us a way to save FatSecret tokens and associate them with individual users:

$rails g model ApiToken provider:string auth_token:string auth_secret:string user_id:integer $rake db:migrate
Create a has_many/belongs_to association between the User and ApiToken models.

Below class User < ActiveRecord::Base in app/models/user.rb add:
has_many :api_tokens

Below class ApiToken < ActiveRecord::Base in app/models/api_token.rb add:
belongs_to :user
Create the ApiTokens controller:

$rails g controller ApiTokens create

Edit app/controllers/api_tokens_controller.rb:

class ApiTokensController < ApplicationController
  before_filter :authenticate_user!
  def create
    auth = omniauth(request.env['omniauth.auth'])
    user_id = request.env['omniauth.params']['user_id']
    origin = request.env['omniauth.origin']

    @user = User.find(user_id)

    @new_api = @user.api_tokens.build(auth)

    if @new_api.save
      redirect_to origin
    end
  end

  private

  def omniauth auth
    params = {
      "provider" => auth['provider'],
      "auth_token" => auth['credentials']['token'],
      "auth_secret" => auth['credentials']['secret']
    }
  end
end

There’s a lot going on here. Let me explain. When our users sign into FatSecret, the FatSecret OmniAuth gem returns a request.env hash to the api_tokens_controller including the provider name, the auth tokens, the user_id, the origin (the route back to where the user started) and a lot more data we’re not using. Check out the Auth Hash Schema doc for more info.

Create the routes and views:

Edit config/routes.rb:

Rails3DeviseRspecCucumber::Application.routes.draw do
  match '/users/:user_id/api_tokens/new' => redirect('/auth/fatsecret?user_id=%{user_id}')
  get '/auth/fatsecret/callback', to: 'api_tokens#create'

  authenticated :user do
    root :to => 'home#index'
  end
  root :to => "home#index"

  devise_for :users
  resources :users do
    resources :api_tokens
  end
end

Edit app/views/users/show.html.erb:

<h3>User</h3>
<p>User: <%= @user.name %></p>
<p>Email: <%= @user.email if @user.email %></p>
<h4>Your APIs</h4>
<ul>
<% user_apis = [] %>
<% @user.api_tokens.each do |api| %>
  <li><b><%= api.provider.camelize %></b>( token: <%= api.auth_token %>, secret: <%= api.auth_secret %>  </li>
  <% user_apis << api.provider %>
<% end %>
<% unless user_apis.include?('fatsecret') %>
  <%= link_to 'Add FatSecret', new_user_api_token_path(@user) %>
<% end %>
</ul>

In the routes, we’ve made :api_tokens a nested resource of :users. This performs some magic for us:

It creates a few named routes, including the new_user_api_token_path we’re using for our ‘Add FatSecret’ link.
It includes the user_id in the route, so we can send that to our api_tokens_controller along with our Fatsecret data.

Done. Get connected to FatSecret!

Start the app $rails s Open http://localhost:3000 in your browser.
Sign up and login as a new user.
Click on your user name.
Click ‘Add Fatsecret’.

You should be redirected to the FatSecret website.
Sign In (if you’re already signed in click ‘Allow’)
You’ll be redirected back to the app. Your FatSecret tokens are saved in the database.

Conclusion

If you were able to follow along, you should have an app that can retrieve FatSecret auth data. If you get stuck or have any questions, leave a comment here or Tweet me @scrawlon.

The next step is using the auth data to connect to the FatSecret REST API and do searches on a user’s behalf. That will be the topic of my next post.

UPDATE Added Part 2 of this tutorial explaining how to make FatSecret API calls.

FatSecret OmniAuth