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The code in this tutorial could be found on samplergthree

How to build a Facebook application within Rails 3 using the RestGraph gem

  1. Before you start, I strongly recommend reading these:

  2. Go to FB Developers website and create a new FB app. Set its canvas name, canvas url and your site URL. Make sure the canvas type is set to "iframe" (which should be the case by default).

  3. Build a new Rails application.

     rails new <name>

  4. Declare RestGraph and its dependencies in the Gemfile. Add these lines:

     gem 'rest-graph'

 # these gems are used in rest-graph
 gem 'rest-client', '>=1.6'
 gem 'json'        # you may also use other JSON parsers/generators, i.e. 'yajl-ruby' or 'json_pure'

    And run:

     bundle install

  5. In order to configure your Rails application for the Facebook application you created, you must create a rest-graph.yaml file in your /config directory and fill it with your Facebook configuration. If you plan to run your application in the Facebook canvas, also provide a canvas name.

    Example:

     development:
     app_id: 'XXXXXXXXXXXXXX'
     secret: 'YYYYYYYYYYYYYYYYYYYYYYYYYYY'
     callback_host: 'my.dev.host.com'

 production:
     app_id: 'XXXXXXXXXXXXXX'
     secret: 'YYYYYYYYYYYYYYYYYYYYYYYYYYY'
     canvas: 'yourcanvasname'
     callback_host: 'my.production.host.com'

    If you push to Heroku, your production callback_host should be yourappname.heroku.com. You can also access your app directly running rails server (or just rails s) in your console, but if you do not have an external IP address (e.g. you are behind a NAT), you will need to use a service called a tunnel in order to make your application accessible to the outer world (and Facebook callbacks). You'll find more information on setting up a tunnel here: http://tunnlr.com/.

  6. Let's create a first controller for your app - ScratchController.

     rails generate controller Scratch

  7. The next step will be to include rest-graph in your controller. You should put this line in:

     include RestGraph::RailsUtil

    Now you can make use of the RestGraph commands :)

  8. To actually use rest-graph in a controller action, you will need to first call "rest_graph_setup", which reads the configuration from the rest-graph.yaml and creates a rest_graph object. Let's set this up in a before_filter.

    Add this line after the include RestGraph::RailsUtil:

     before_filter :filter_setup_rest_graph

    And declare filter_setup_rest_graph as a private function:

     private

 def filter_setup_rest_graph
     rest_graph_setup(:auto_authorize => true)
 end

    The :auto_authorize argument of rest_graph_setup tells RestGraph to redirect users to the app authorization page if the app is not authorized yet.

    Hooray! You can now perform all kinds of Graph API operations using the rest_graph object.

  9. Let's start with following sample action in the Scratch controller:

     def me
     render :text => rest_graph.get('me').inspect
 end

  10. To run this, go to the /config/routes.rb file to set up the default routing. For now you will just need this line:

    match ':controller/:action'

  11. Commit your change in git, and then push to Heroku:

    git add .
git commit -m "first test of rest-graph using scratch/me"
git push heroku master

    After you push your app to Heroku, you can open http://yourappname.heroku.com/scratch/me in your browser. If you are not yet logged into Facebook, it will ask you to log in. If you are logged in your Facebook account, this address should redirect you to the authorization page and ask if you want to let your application access your public information. After you confirm, you should be redirected back to 'scratch/me' action which will show your basic information.

  12. To see other information, such as your home feed, is very easy. You can add another sample action to your controller:

    def feed
    render :text => rest_graph.get('me/home').inspect
end

    If you will push the changes to Heroku and go to http://yourappname.heroku.com/scratch/feed, the page should display a JSON hash with all the data from your Facebook home feed.

  13. Now let's try to access your Facebook wall. You need to add a new action to your controller:

    def wall
    render :text => rest_graph.get('me/feed').inspect
end

    Note that Facebook's naming is such that your home news feeds is accessed via me/home and your profile walls is accessed via me/feed ...

    Actually, I need to warn you that this time the action won't work properly. Why? Because users didn't grant you the permission to access their walls! You need to ask them for this special permission and that means you need to add something more to your controller.

    So, we will organize all the permissions we need as a scope and pass them to the rest_graph_setup call. I find it handy to make the scope array and declare what kind of permissions I need just inside this array. If you feel it's a good idea, you can add this line to your private setup function, just before you call rest_graph_setup:

    scope = []
scope << 'read_stream'

    The only permission you need right now is the 'read_stream' permission. You can find out more about different kinds of user permissions here: http://developers.facebook.com/docs/authentication/permissions/

    You also need to add the auto_authorize_scope argument to the rest_graph_setup. It will look this way now:

    rest_graph_setup(:auto_authorize => true, :auto_authorize_scope => scope.join(','))

    As you see, you might as well pass the argument like this :auto_authorize_scope => 'read_stream', but once you have to get a lot of different permissions, it's very useful to put them all in an array, because it's more readable and you can easily delete or comment out any one of them.

    Now save your work and push it to Heroku or just try in your tunneled development environment. /scratch/wall URL should give you the hash with user's wall data now!

    Remember. Anytime you need to get data of a new kind, you need to ask user for a certain permission first and that means you need to declare this permission in your scope array!

  14. What else? If you know how to deal with hashes then you will definitely know how to get any kind of data you want using the rest_graph object. Let's say you want to get a last object from a user's wall (last in terms of time, last posted, so the first on the wall and therefore first to Ruby). Let's take a look at the /scratch/feed page. The hash which is printed on this page has 2 keys - data and paging. Let's leave the paging key aside. What's more interesting here comes as a value of 'data'. So the last object in any user's wall will be simply:

    rest_graph.get('me/feed')['data'].first

    Now let's say you want only to keep the name of the author of this particular object. You can get it by using:

    rest_graph.get('me/feed')['data'].first['from']['name']

    That's it!

  15. More information on customizing RestGraph and its functions are to be found here: https://github.com/godfat/rest-graph