Rails + OmniAuth Facebook: how to obtain Access Token? - ruby-on-rails

Question

I am trying to fetch the list of friends from Facebook. Sign in through Facebook is not a problem, but the problem is to fetch person's friends - because of access token.
puts request.env["omniauth.auth"].inspect
puts '==='
#user = User.find_for_facebook_oauth(request.env["omniauth.auth"], current_user)
#fb_user = FbGraph::User.fetch(#user.uid).friends
puts #fb_user.inspect
The problem is on the #4 line - in this case I am getting error
OAuthException :: An access token is required to request this resource.
When I put there something like this:
#fb_user = FbGraph::User.fetch(request.env["omniauth.auth"].credentials.token).friends
I'll get
OAuthException :: (#803) Some of the aliases you requested do not exist: PRINTED OUT TOKEN
What's the proper way to obtain the access token?
EDIT: Current flow
class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController
def facebook
#user = User.find_for_facebook_oauth(request.env["omniauth.auth"], current_user)
#fb_user = FbGraph::User.fetch(request.env["omniauth.auth"].credentials.token).friends
if !#user
flash[:error] = 'This email address is already used in the system.'
redirect_to :back
elsif #user.persisted?
flash[:notice] = I18n.t "devise.omniauth_callbacks.success", :kind => "Facebook"
sign_in_and_redirect #user, :event => :authentication
else
session["devise.facebook_data"] = request.env["omniauth.auth"]
redirect_to new_user_registration_url
end
end
In User model:
def self.find_for_facebook_oauth(access_token, signed_in_resource=nil)
data = access_token.extra.raw_info
if user = User.where(:provider => 'facebook', :uid => data.id).first
user
elsif user = User.where('email = ? AND provider IS NULL', data.email).first
return false
else
...saving data...
end
return user if user
end

Answer 1

You can get an access token for test purposes via the Facebook Graph API Explorer. Make sure you select the proper fields that you want access to, and click "get access token". A more permanent solution is to register your app with Facebook so that you will be able to continually make requests without the token dying.
You should look into the Facebook OAuth dialogue.
I'm assuming you're trying to use the OAuth2 strategy instead of the Javascript SDK. Make sure you have set up a callback url like so:
client.redirect_uri = "http://your.client.com/facebook/callback"
In the controller that handles your callback, you should do something like this:
client.authorization_code = params[:code]
access_token = client.access_token! :client_auth_body
FbGraph::User.me(access_token).fetch
Make sure you've let fb_graph know what your app's id and secret are. You should look into this stackoverflow to keep your apps info safe.
I'll also plug the koala gem