Google API for Blogger 3.0 error - ruby

Question

I am trying to run sample code in Ruby to fetch blog posts list using Google's APIs for Blogger 3.0. This is the code:
require 'rubygems'
require 'google/api_client'
require 'sinatra'
require 'google/api_client'
require 'logger'
enable :sessions
def logger; settings.logger end
def api_client; settings.api_client; end
def blogger_api; settings.blogger; end
def user_credentials
# Build a per-request oauth credential based on token stored in session
# which allows us to use a shared API client.
#authorization ||= (
auth = api_client.authorization.dup
auth.redirect_uri = to('/oauth2callback')
auth.update_token!(session)
auth
)
end
configure do
log_file = File.open('blogger.log', 'a+')
log_file.sync = true
logger = Logger.new(log_file)
logger.level = Logger::DEBUG
client = Google::APIClient.new
client.authorization.client_id = 'XXXXXXXXXXXXX'
client.authorization.client_secret = 'XXXXXXXXXXXXX'
client.authorization.scope = 'https://www.googleapis.com/auth/blogger'
blogger = client.discovered_api('blogger', 'v3')
set :logger, logger
set :api_client, client
set :blogger, blogger
end
before do
# Ensure user has authorized the app
unless user_credentials.access_token || request.path_info =~ /^\/oauth2/
redirect to('/oauth2authorize')
end
end
after do
# Serialize the access/refresh token to the session
session[:access_token] = user_credentials.access_token
session[:refresh_token] = user_credentials.refresh_token
session[:expires_in] = user_credentials.expires_in
session[:issued_at] = user_credentials.issued_at
end
get '/oauth2authorize' do
# Request authorization
redirect user_credentials.authorization_uri.to_s, 303
end
get '/oauth2callback' do
# Exchange token
user_credentials.code = params[:code] if params[:code]
user_credentials.fetch_access_token!
redirect to('/')
end
get '/' do
# Fetch list of posts
result = api_client.execute(:api_method => settings.blogger.posts.list, :parameters => {'blogId' => 'XXXXXXXXXXXXX'})
[result.status, {'Content-Type' => 'application/json'}, result.data.to_json]
end
When I connect to the running local application (after authorized it) I can see this "sinatra" error:
#<NameError: undefined local variable or method `blogger' for #<Sinatra::Application:0x92ac2dc>>
It is a bit obscure to me. Any idea?