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Sinatra: Frequently Asked Questions
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Frequently Asked Questions

  • this will become the toc {:toc}

How do I make my Sinatra app reload on changes? {#reloading}

First off, in-process code reloading in Ruby is hard and having a solution that works for every scenario is technically impossible.

Which is why we recommend you to do out-of-process reloading.

First you need to install rerun if you haven't already:

$ gem install rerun

Now if you start your Sinatra app like this:

$ ruby app.rb

All you have to do for reloading is instead do this:

$ rerun 'ruby app.rb'

If you are for instance using rackup, instead do the following:

$ rerun 'rackup'

You get the idea.

If you still want in-process reloading, check out Sinatra::Reloader.

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 to('/bar')
end

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

See the Sinatra README on how to set additional parameters for sessions, like the session secret or expiration date.

You can also use Rack::Session::Cookie directly instead of enable :sessions (example from Rack documentation):

use Rack::Session::Cookie, :key => 'rack.session',
                           :domain => 'foo.com',
                           :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         # => 'https://example.com/hello-world?foo=bar'
end

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)
    "<em>#{text}</em>"
  end
end

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

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 %>

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

Sure:

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

Seriously.

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

Put a question mark after it:

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

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'
end

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
end

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

Try starting Thin with the --debug argument:

thin --debug --rackup config.ru 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 => '[email protected]',
            :from => '[email protected]',
            :subject => 'Howdy, Partna!'
end

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

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

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

Frank

And in mailerapp.rb:

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

How do I escape HTML? {#escape_html}

Use Rack::Utils in your helpers as follows:

helpers do
  def h(text)
    Rack::Utils.escape_html(text)
  end

  def hattr(text)
    Rack::Utils.escape_path(text)
  end
end

Now you can escape HTML entities inside outputted text in your templates in one of two ways:

<div><%= h scary_output %></div>

or using the <%== feature:

<div><%== scary_output %></div>

And you can escape text inside element attributes in your templates like this:

<a href="<%= hattr scary_output %>" >A nice safe link!</a>

Thanks to Chris Schneider for the tip!

How do I automatically escape HTML? {#auto_escape_html}

Require Erubis or Erubi and set escape_html to true:

require 'erubis' # or 'erubi'
set :erb, :escape_html => true

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

get '/' do
  erb :index
end

Read more on the Tilt Google Group 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 = Logger.new(STDOUT)
    ActiveRecord::Migration.verbose = true
    ActiveRecord::Migrator.migrate("db/migrate")
  end
end

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.)

For another option, check out the Sinatra ActiveRecord Extension.

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 'sinatra'

use Rack::Auth::Basic, "Restricted Area" do |username, password|
  username == 'admin' and password == 'admin'
end

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

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

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 'sinatra'

helpers do
  def protected!
    return if authorized?
    headers['WWW-Authenticate'] = 'Basic realm="Restricted Area"'
    halt 401, "Not authorized\n"
  end

  def authorized?
    @auth ||=  Rack::Auth::Basic::Request.new(request.env)
    @auth.provided? and @auth.basic? and @auth.credentials and @auth.credentials == ['admin', 'admin']
  end
end

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

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

How do I test HTTP authentication? {#test_http_auth}

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

require 'sinatra'

use Rack::Auth::Basic do |username, password|
  username == 'admin' and password == 'admin'
end

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

You can test it like this with Rack::Test:

ENV['APP_ENV'] = 'test'
require 'test/unit'
require 'rack/test'

require 'application'

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

  def app
    Sinatra::Application
  end

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

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

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