Although HTTP is itself a stateless protocol, one way to maintain the state for a user is through the use of cookie-based sessions, demonstrated in Example 2-33. In this approach, a cookie (in this case, one named rack.session) is stored client-side and used to house data related to the activity in the current user’s session.

You can enable sessions via the configure block. Once enabled, the session object can be used to store and retrieve values.

require 'sinatra'

configure do
  enable :sessions
end

before do
  content_type :txt
end

get '/set' do
  session[:foo] = Time.now
  "Session value set."
end

get '/fetch' do
  "Session value: #{session[:foo]}"
end