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Sinatra: Frequently Asked Questions

Frequently Asked Questions

  • this will become the toc {:toc}

What are my deployment options? {#deploy}

See the book.

How do I use sessions? {#sessions}

Sessions are disabled by default. You need to enable them and then use the session hash from routes and views:

enable :sessions

get '/foo' do
  session[:message] = 'Hello World!'
  redirect '/bar'

get '/bar' do
  session[:message]   # => 'Hello World!'

If you need to set additional parameters for sessions, like expiration date, use Rack::Session::Cookie directly instead of enable :sessions (example from Rack documentation):

use Rack::Session::Cookie, :key => 'rack.session',
                           :domain => '',
                           :path => '/',
                           :expire_after => 2592000, # In seconds
                           :secret => 'change_me'

How do I use session-based flash? {#flash}

Use Rack::Flash.

Can I run Sinatra under Ruby 1.9? {#ruby19}

Not yet. Rack is not yet Ruby 1.9 compatible and Sinatra is very much dependent on Rack. We are in the early stages of testing under 1.9 and we're reviewing all new code and idioms for potential 1.9 compatibility issues. The 1.0 release (currently scheduled for mid 2009) will run on 1.9 and chances are good that we'll support 1.9 before then.

How do I get the "route" for the current page? {#path_info}

The request object probably has what you're looking for:

get '/hello-world' do
  request.path_info   # => '/hello-world'
  request.fullpath    # => '/hello-world?foo=bar'
  request.url         # => ''

See Rack::Request for a detailed list of methods supported by the request object.

How do I access helpers from within my views? {#helpview}

Call them! Views automatically have access to all helper methods. In fact, Sinatra evaluates routes, views, and helpers within the same exact object context so they all have access to the same methods and instance variables.

In hello.rb:

helpers do
  def em(text)

get '/hello' do
  @subject = 'World'
  haml :hello

In views/hello.haml:

%p= "Hello " + em(@subject)

How do I render partials? {#partials}

Sinatra's template system is simple enough that it can be used for page and fragment level rendering tasks. The erb and haml methods simply return a string. However, you need to make sure you disable layout rendering as follows:

<%= erb(:mypartial, :layout => false) %>

See Chris Schneider's partials.rb for a more robust partials implementation. It even supports rendering collections.

Can I have multiple URLs trigger the same route/handler? {#multiroute}


["/foo", "/bar", "/baz"].each do |path|
  get path do
    "You've reached me at #{request.path_info}"


How do I make the trailing slash optional? {#slash}

Put a question mark after it:

get '/foo/bar/?' do
  "Hello World"

The route matches "/foo/bar" and "/foo/bar/".

How do I render templates nested in subdirectories? {#subdir}

Sinatra apps do not typically have a very complex file hierarchy under views. First, consider whether you really need subdirectories at all. If so, you can use the views/foo/bar.haml file as a template with:

get '/' do
  haml :'foo/bar'

This is basically the same as sending #to_sym to the filename and can also be written as:

get '/' do
  haml 'foo/bar'.to_sym

I'm running Thin and an error occurs but there's no output {#thindebug}

Try starting Thin with the --debug argument:

thin --debug --rackup start

That should give you an exception and backtrace on stderr.

How do I send Email from Sinatra? {#email}

How about a Pony (sudo gem install pony):

require 'pony'
post '/signup' do
  Pony.mail :to => '',
    :from => '',
    :subject => 'Howdy, Partna!'

You can even use templates to render the body. In email.erb:

Good day <%= params[:name] %>,

Thanks for my signing my guestbook. You're a doll.


And in mailerapp.rb:

post '/guestbook/sign' do
  Pony.mail :to => params[:email],
    :from => "",
    :subject => "Thanks for signing my guestbook, #{params[:name]}!",
    :body => erb(:email)

How do I escape html? {#escape_html}

Include Rack::Utils in your helpers and create an h alias as follows:

helpers do
  include Rack::Utils
  alias_method :h, :escape_html

Now you can escape html in your templates like this:

<%= h scary_output %>

Thanks to Chris Schneider for the tip!

How do I use ActiveRecord migrations? {#ar-migrations}

From Adam Wiggins's blog:

To use ActiveRecord’s migrations with Sinatra (or other non-Rails project), add the following to your Rakefile:

namespace :db do
  desc "Migrate the database"
    task(:migrate => :environment) do
    ActiveRecord::Base.logger =
    ActiveRecord::Migration.verbose = true

This assumes you have a task called :environment which loads your app’s environment (requires the right files, sets up the database connection, etc).

Now you can create a directory called db/migrate and fill in your migrations. I usually call the first one 001_init.rb. (I prefer the old sequential method for numbering migrations vs. the datetime method used since Rails 2.1, but either will work.)

How do I use HTTP authentication? {#auth}

You have at least two options for implementing basic access authentication (Basic HTTP Auth) in your application.

I. When you want to protect all requests in the application, simply put Rack::Auth::Basic middleware in the request processing chain by the use directive:

require 'rubygems'
require 'sinatra'

use Rack::Auth::Basic do |username, password|
  [username, password] == ['admin', 'admin']

get '/' do
  "You're welcome"

get '/foo' do
  "You're also welcome"

II. When you want to protect only certain URLs in the application, or want the authorization to be more complex, you may use something like this:

require 'rubygems'
require 'sinatra'

helpers do

  def protected!
    response['WWW-Authenticate'] = %(Basic realm="Testing HTTP Auth") and \
    throw(:halt, [401, "Not authorized\n"]) and \
    return unless authorized?

  def authorized?
    @auth ||=
    @auth.provided? && @auth.basic? && @auth.credentials && @auth.credentials == ['admin', 'admin']


get '/' do
  "Everybody can see this page"

get '/protected' do
  "Welcome, authenticated client"

How do I test HTTP authentication? {#test_http_auth}

Assuming you have this simple implementation of HTTP authentication in your application:

require 'rubygems'
require 'sinatra'

use Rack::Auth::Basic do |username, password|
  [username, password] == ['admin', 'admin']

get '/protected' do
  "You're welcome"

You can test it like this:

require 'rubygems'
require 'sinatra'
require 'sinatra/test/unit'
require 'application'
require 'base64'

class ApplicationTest < Test::Unit::TestCase

  def test_without_authentication
    get '/protected'
    assert_equal 401, @response.status

  def test_with_bad_credentials
    get '/protected', {}, {'HTTP_AUTHORIZATION' => encode_credentials('go', 'away')}
    assert_equal 401, @response.status

  def test_with_proper_credentials
    get '/protected', {}, {'HTTP_AUTHORIZATION'=> encode_credentials('admin', 'admin')}
    assert_equal 200, @response.status
    assert_equal "You're welcome", @response.body


  def encode_credentials(username, password)
    "Basic " + Base64.encode64("#{username}:#{password}")