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Sinatra: Frequently Asked Questions

Frequently Asked Questions

  • this will become the toc {:toc}

What happened to reloading in Sinatra 0.9.2? {#reloading}

Source file reloading was removed in the 0.9.2 due to excess complexity.

For reloading Sinatra we recommend either using the reloader or shotgun.

The reloader will reload single files that changed, whereas shotgun will restart the HTTP server on every request. See "Reloading Ruby Code" to learn more about the differences.

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}

Yes. As of Sinatra 0.9.2, Sinatra is fully Ruby 1.9 and Rack 1.0 compatible. Since 1.1 you do not have to deal with encodings on your own, unless you want to.

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.

Since Sinatra 1.1, you can use the same calls for partials you use in the routes:

<%= erb :mypartial %>

In versions prior to 1.1, you need to make sure you disable layout rendering as follows:

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

See Sam Elliott and Iain Barnett's Sinatra-Partial extension for a more robust partials implementation. It also supports rendering collections and partials in subdirectories.

The code used to live in a gist, but we have put it in a gem so we can maintain it properly and provide an easier way for developers to include its behaviour. It was adapted from Chris Schneider's original partials.rb implementation.

Use it as follows to render the mypartial.haml(1) or the admin/mypartial.haml(2) partials, or with a collection (3) & (4):

<%= partial(:mypartial) %> <!--(1)-->
<%= partial(:'admin/mypartial') %> <!--(2)-->
<%= partial(:object, :collection => @objects) %> <!--(3)-->
<%= partial(:'admin/object', :collection => @objects) %> <!--(4)-->

In (1) & (2), the partial will be rendered plain from their files, with no local variables (specify them with a hash passed into :locals). In (3) & (4), the partials will be rendered, populating the local variable object with each of the objects from the collection.

It is also possible to enable using underscores, a la Rails, and to choose a different rendering engine from haml.

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 automatically escape html? {#auto_escape_html}

Require Erubis and set escape_html to true:

require 'erubis'
set :erubis, :escape_html => true

Then, any templates rendered with Erubis will be automatically escaped:

get '/' do
  erubis :index

Read more on the Tilt Google Group and see this example app for details.

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, "Restricted Area" 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!
    unless authorized?
      response['WWW-Authenticate'] = %(Basic realm="Restricted Area")
      throw(:halt, [401, "Not authorized\n"])

  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.rb:

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 with Rack::Test:

ENV['RACK_ENV'] = 'test'

require 'rubygems'
require 'test/unit'
require 'rack/test'

require 'application'

class ApplicationTest < Test::Unit::TestCase
  include Rack::Test::Methods

  def app

  def test_without_authentication
    get '/protected'
    assert_equal 401, last_response.status

  def test_with_bad_credentials
    authorize 'bad', 'boy'
    get '/protected'
    assert_equal 401, last_response.status

  def test_with_proper_credentials
    authorize 'admin', 'admin'
    get '/protected'
    assert_equal 200, last_response.status
    assert_equal "You're welcome", last_response.body
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