Fbsync

This gem is a simple Rails lib to enable easy fetching of Facebook data, assuming you need to run some background job that synchronizes some facebook account with your app data.

This is clearly meant to cover the following case :

• You have one facebook account to synchronize your app (website) with
• You must fetch data from facebook and be warned when your admin's token is expired or will expire soon, so the admin can refresh it manually
• You want to use FbGraph to work with Facebook's API

Installation

Add the gem to your app's Gemfile and bundle install :

gem "fbsync"

Run the install generator to get migrations and initializer in your app, and migrate :

rails generate fbsync:install
rake db:migrate

Using the Fbsync::Token model

Basics

The Token model is meant to be a container for your token. The idea behind it is to feed it a short-lived token and when you save the model it fetches a long-lived token from Facebook's API and store it.

The way you get the short-lived token doesn't matter. For instance, say you signed in you user from facebook through omniauth, you can do the following in your omniauth callback :

class OmniauthCallbacksController
  def facebook
    token = FbSync::Token.create(value: request.env["omniauth.auth"].credentials.token)
    # Here the Token instance is saved with a long-lived token contained in #value
    # so you can use it to query Facebook API for 2 months
  end
end

Associate a user to a token

The Fbsync::Token model is ready to be associated to a token_owner, say a User model through a polymorphic association :

# app/models/user.rb
class User < ActiveRecord::Base
  has_one :token, as: :token_owner, class_name: 'Fbsync::Token'
end

Then in your omniauth callback you can store it as the following :

class OmniauthCallbacksController
  def facebook
    current_user.create_token FbSync::Token.create(value: request.env["omniauth.auth"].credentials.token)
    # You can now access your token with `current_user.token`
  end
end

Defining a default method to fetch a token

If you don't want to manually fetch the token in your tasks and you only have one admin with a token, you can set the following property in the fbsync initializer :

Fbsync.config do |config|
  config.token_fetch_method = lambda {
    # Here we assume you have a single admin with an associated token
    User.includes(:token).where('admin = ? AND fbsync_tokens.id NOT NULL', true).first.token
  }
end

Using the Fbsync::Sync#run method

The goal of all this configuration, is to allow you to run operations with a long-lived token and warn the admin of a posible expiration of his token.

Say you want to run some job with a Rake task, you could do the following :

namespace :facebook do
  task fetch_albums: :environment do
    FbSync::Sync.run do |token|
      # Use the long-lived token here
    end
  end
end