Sinatra

Sinatra is a DSL for quickly creating web-applications in Ruby with minimal effort.

Sample App

# myapp.rb
require 'rubygems'
require 'sinatra'
get '/' do
  'Hello world!'
end

Run with ruby myapp.rb and view at http://localhost:4567

HTTP Methods

get '/' do
  .. show things ..
end

post '/' do
  .. create something ..
end

put '/' do
  .. update something ..
end

delete '/' do
  .. annihilate something ..
end

head '/' do

end

NOTE: put and delete are also triggered when a _method parameter is set to PUT or DELETE and the HTTP request method is POST

Routes

Routes are matched based on the order of declaration. The first route that matches the request is invoked.

Simple:

get '/hi' do
  ...
end

Named parameters:

get '/:name' do
  # matches /sinatra and the like and sets params[:name]
end

Splat parameters:

get '/say/*/to/*' do
  # matches /say/hello/to/world
  params["splat"] # => ["hello", "world"]
end

get '/download/*.*' do
  # matches /download/path/to/file.xml
  params["splat"] # => ["path/to/file", "xml"]
end

User agent matching:

get '/foo', :agent => /Songbird (\d\.\d)[\d\/]*?/ do
  "You're using Songbird version #{params[:agent][0]}"
end

get '/foo' do
  # matches non-songbird browsers
end

Static files

Put all of your static content in the ./public directory

root
  \ public

If a file exists that maps to the REQUEST_PATH then it is served and the request ends. Otherwise, Sinatra will look for an event that matches the path.

Views

Views are searched for in a “views” directory in the same location as your main application.

Haml Templates

get '/' do
  haml :index
end

Renders ./views/index.haml.

Erb

get '/' do
  erb :index
end

Renders ./views/index.erb

Builder

See Sinatra::Builder

Sass

get '/stylesheet.css' do
  content_type 'text/css', :charset => 'utf-8'
  sass :stylesheet
end

Renders ./views/stylesheet.sass.

Inline Templates

get '/' do
  haml '%div.title Hello World'
end

Renders the inlined template string.

Accessing Variables

Templates are evaluated within the Sinatra::EventContext instance used to evaluate event blocks. Instance variables set in event blocks can be accessed direcly in views:

get '/:id' do
  @foo = Foo.find(params[:id])
  haml '%h1= @foo.name'
end

Or, specify an explicit Hash of local variables:

get '/:id' do
  foo = Foo.find(params[:id])
  haml '%h1= foo.name', :locals => { :foo => foo }
end

This is typically used when rendering templates as partials from within other templates.

In-file Templates

Templates may be defined at the end of the source file:

get '/' do
  haml :index
end

use_in_file_templates!

It’s also possible to define named templates using the top-level template method:

template :layout do
  "X\n=yield\nX"
end

template :index do
  '%div.title Hello World!'
end

get '/' do
  haml :index
end

Helpers

The top-level helpers method takes a block and extends all EventContext instances with the methods defined:

helpers do
  def bar(name)
    "#{name}bar"
  end
end

get '/:name' do
  bar(params[:name])
end

Filters

These are run in Sinatra::EventContext before every event.

before do
  .. this code will run before each event ..
end

Halt!

To immediately stop a request during a before filter or event use:

throw :halt

Set the body to the result of a helper method

throw :halt, :helper_method

Set the body to the result of a helper method after sending it parameters from the local scope

throw :halt, [:helper_method, foo, bar]

Set the body to a simple string

throw :halt, 'this will be the body'

Set status then the body

throw :halt, [401, 'go away!']

Set the status then call a helper method with params from local scope

throw :halt, [401, [:helper_method, foo, bar]]

Run a proc inside the Sinatra::EventContext instance and set the body to the result

throw :halt, lambda { puts 'In a proc!'; 'I just wrote to $stdout!' }

Create you own to_result

class MyResultObject
  def to_result(event_context, *args)
    event_context.body = 'This will be the body!
  end
end

get '/' do
  throw :halt, MyResultObject.new
end

Get the gist? If you want more fun with this then checkout to_result on Array, Symbol, Fixnum, NilClass.

Configuration and Reloading

Sinatra supports multiple environments and reloading. Reloading happens before every request when running under the :development environment. Wrap your configurations in configure (i.e. Database connections, Constants, etc.) to protect them from reloading or to target specific environments.

All environments:

configure do
  ...
end

Production:

configure :production do
  ...
end

Two at a time:

configure :production, :test do
  ...
end

This is also really nifty for error handling.

Error handling

Error handlers run inside the current Sinatra::EventContext instance, which means you get all the goodies it has to offer (i.e. haml, erb, throw :halt, etc.)

Not Found

When Sinatra::NotFound is raised, the not_found handler is invoked:

not_found do
  'This is nowhere to be found'
end

Error

By default, the error handler is invoked on Sinatra::ServerError or when an unknown error occurs.

The exception can be obtained from the ‘sinatra.error’ variable in request.env.

error do
  'Sorry there was a nasty error - ' + request.env['sinatra.error'].name
end

Custom errors:

error MyCustomError do
  'So what happened was...' + request.env['sinatra.error'].message
end

Then, if this happens:

get '/' do
  raise MyCustomError, 'something bad'
end

You get this:

So what happened was... something bad

Sinatra installs special not_found and error handlers when running under the development.

Mime types

When using send_file or static files you may have mime types Sinatra doesn’t understand. Use mime in those cases.

mime :foo, 'text/foo'

Rack Middleware

Sinatra rides on Rack, a minimal standard interface for Ruby web frameworks. One of Rack’s most interesting capabilities for application developers is support for “middleware” – components that sit between the server and your application monitoring and/or manipulating the HTTP request/response to provide various types of common functionality.

Sinatra makes building Rack middleware pipelines a cinch via a top-level use method:

require 'sinatra'
require 'my_custom_middleware'

use Rack::Lint
use MyCustomMiddleware

get '/hello' do
  'Hello World'
end

The semantics of use are identical to those defined for the Rack::Builder DSL (most frequently used from rackup files). For example, the use method accepts multiple/variable args as well as blocks:

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

Rack is distributed with a variety of standard middleware for logging, debugging, URL routing, authentication, and session handling. Sinatra uses many of of these components automatically based on configuration so you typically don’t have to use them explicitly.

Testing

Test/Unit

require 'rubygems'
require 'sinatra'
require 'sinatra/test/unit'
require 'my_sinatra_app'

class MyAppTest < Test::Unit::TestCase

  def test_my_default
    get_it '/'
    assert_equal 'My Default Page!', @response.body
  end

  def test_with_agent
    get_it '/', :agent => 'Songbird'
    assert_equal 'You're in Songbird!', @response.body
  end

  ...

end

Test/Spec

require 'rubygems'
require 'sinatra'
require 'sinatra/test/spec'
require 'my_sinatra_app'

describe 'My app' do

  it "should show a default page" do
    get_it '/'
    should.be.ok
    body.should.equal 'My Default Page!'
  end

  ...

end

RSpec

require 'rubygems'
require 'spec'
require 'sinatra'
require 'sinatra/test/rspec'
require 'my_sinatra_app'

describe 'My app' do
  it 'should show a default page' do
    get_it '/'
    @response.should be_ok
    @response.body.should == 'My Default Page!'
  end

  ...

end

See Sinatra::Test::Methods for more information on get_it, post_it, put_it, and friends.

Command line

Sinatra applications can be run directly:

ruby myapp.rb [-h] [-x] [-p PORT] [-e ENVIRONMENT]

Options are:

-h # help
-p # set the port (default is 4567)
-e # set the environment (default is development)
-x # turn on the mutex lock (default is off)

Contributing

Tools

Besides Ruby itself, you only need a text editor, preferably one that supports Ruby syntax hilighting. VIM and Emacs are a fine choice on any platform, but feel free to use whatever you’re familiar with.

Sinatra uses the Git source code management system. If you’re unfamiliar with Git, you can find more information and tutorials on git.or.cz/ as well as git-scm.com/. Scott Chacon created a great series of introductory screencasts about Git, which you can find here: www.gitcasts.com/

First Time: Cloning The Sinatra Repo

cd where/you/keep/your/projects
git clone git://github.com/bmizerany/sinatra.git
cd sinatra
cd path/to/your_project
ln -s ../sinatra/

Updating Your Existing Sinatra Clone

cd where/you/keep/sinatra
git pull

Using Edge Sinatra in Your App

at the top of your sinatra_app.rb file:

$:.unshift File.dirname(__FILE__) + '/sinatra/lib'
require 'sinatra'

get '/about' do
  "I'm running on Version " + Sinatra::VERSION
end

Contributing a Patch

There are several ways to do this. Probably the easiest (and preferred) way is to fork Sinatra on GitHub (github.com/bmizerany/sinatra), push your changes to your Sinatra repo, and then send Blake Mizerany (bmizerany on GitHub) a pull request.

You can also create a patch file and attach it to a feature request or bug fix on the issue tracker (see below) or send it to the mailing list (see Community section).

Issue Tracking and Feature Requests

sinatra.lighthouseapp.com/

Community

Mailing List

groups.google.com/group/sinatrarb

If you have a problem or question, please make sure to include all the relevant information in your mail, like the Sinatra version you’re using, what version of Ruby you have, and so on.

IRC Channel

You can find us on the Freenode network in the channel #sinatra (chat.freenode.net/#sinatra)

There’s usually someone online at any given time, but we cannot pay attention to the channel all the time, so please stick around for a while after asking a question.