Sinatra
Sinatra is a DSL for quickly creating web applications in Ruby with minimal effort:
# myapp.rb
require 'sinatra'
get '/' do
'Hello world!'
end
Install the gem and run with:
gem install sinatra
ruby -rubygems myapp.rb
View at: localhost:4567
It is recommended to also run gem install thin
, which Sinatra will pick up if available.
Routes
In Sinatra, a route is an HTTP method paired with a URL-matching pattern. Each route is associated with a block:
get '/' do
.. show something ..
end
post '/' do
.. create something ..
end
put '/' do
.. update something ..
end
delete '/' do
.. annihilate something ..
end
options '/' do
.. appease something ..
end
Routes are matched in the order they are defined. The first route that matches the request is invoked.
Route patterns may include named parameters, accessible via the params
hash:
get '/hello/:name' do
# matches "GET /hello/foo" and "GET /hello/bar"
# params[:name] is 'foo' or 'bar'
"Hello #{params[:name]}!"
end
You can also access named parameters via block parameters:
get '/hello/:name' do |n|
"Hello #{n}!"
end
Route patterns may also include splat (or wildcard) parameters, accessible via the params[:splat]
array:
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
Route matching with Regular Expressions:
get %r{/hello/([\w]+)} do
"Hello, #{params[:captures].first}!"
end
Or with a block parameter:
get %r{/hello/([\w]+)} do |c|
"Hello, #{c}!"
end
Conditions
Routes may include a variety of matching conditions, such as the user agent:
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
Other available conditions are host_name
and provides
:
get '/', :host_name => /^admin\./ do
"Admin Area, Access denied!"
end
get '/', :provides => 'html' do
haml :index
end
get '/', :provides => ['rss', 'atom', 'xml'] do
builder :feed
end
You can easily define your own conditions:
set(:probability) { |value| condition { rand <= value } }
get '/win_a_car', :probability => 0.1 do
"You won!"
end
get '/win_a_car' do
"Sorry, you lost."
end
Return Values
The return value of a route block determines at least the response body passed on to the HTTP client, or at least the next middleware in the Rack stack. Most commonly, this is a string, as in the above examples. But other values are also accepted.
You can return any object that would either be a valid Rack response, Rack body object or HTTP status code:
-
An Array with three elements:
[status (Fixnum), headers (Hash), response body (responds to #each)]
-
An Array with two elements:
[status (Fixnum), response body (responds to #each)]
-
An object that responds to
#each
and passes nothing but strings to the given block -
A Fixnum representing the status code
That way we can, for instance, easily implement a streaming example:
class Stream
def each
100.times { |i| yield "#{i}\n" }
end
end
get('/') { Stream.new }
Custom Route Matchers
As shown above, Sinatra ships with built-in support for using String patterns and regular expressions as route matches. However, it does not stop there. You can easily define your own matchers:
class AllButPattern
Match = Struct.new(:captures)
def initialize(except)
@except = except
@captures = Match.new([])
end
def match(str)
@captures unless @except === str
end
end
def all_but(pattern)
AllButPattern.new(pattern)
end
get all_but("/index") do
# ...
end
Note that the above example might be over-engineered, as it can also be expressed as:
get // do
pass if request.path_info == "/index"
# ...
end
Or, using negative look ahead:
get %r{^(?!/index$)} do
# ...
end
Static Files
Static files are served from the ./public
directory. You can specify a different location by setting the :public
option:
set :public, File.dirname(__FILE__) + '/static'
Note that the public directory name is not included in the URL. A file ./public/css/style.css
is made available as http://example.com/css/style.css
.
Views / Templates
Templates are assumed to be located directly under the ./views
directory. To use a different views directory:
set :views, File.dirname(__FILE__) + '/templates'
One important thing to remember is that you always have to reference templates with symbols, even if they’re in a subdirectory (in this case, use :'subdir/template'
). You must use a symbol because otherwise rendering methods will render any strings passed to them directly.
Haml Templates
The haml
gem/library is required to render HAML templates:
# You'll need to require haml in your app
require 'haml'
get '/' do
haml :index
end
Renders ./views/index.haml
.
Haml’s options can be set globally through Sinatra’s configurations, see Options and Configurations, and overridden on an individual basis.
set :haml, :format => :html5 # default Haml format is :xhtml
get '/' do
haml :index, :format => :html4 # overridden
end
Erb Templates
# You'll need to require erb in your app
require 'erb'
get '/' do
erb :index
end
Renders ./views/index.erb
.
Erubis Templates
The erubis
gem/library is required to render Erubis templates:
# You'll need to require erubis in your app
require 'erubis'
get '/' do
erubis :index
end
Renders ./views/index.erubis
.
It is also possible to replace Erb with Erubis:
require 'erubis'
Tilt.register :erb, Tilt[:erubis]
get '/' do
erb :index
end
Renders ./views/index.erb
with Erubis.
Builder Templates
The builder
gem/library is required to render builder templates:
# You'll need to require builder in your app
require 'builder'
get '/' do
builder :index
end
Renders ./views/index.builder
.
Nokogiri Templates
The nokogiri
gem/library is required to render nokogiri templates:
# You'll need to require nokogiri in your app
require 'nokogiri'
get '/' do
nokogiri :index
end
Renders ./views/index.nokogiri
.
Sass Templates
The haml
or sass
gem/library is required to render Sass templates:
# You'll need to require haml or sass in your app
require 'sass'
get '/stylesheet.css' do
sass :stylesheet
end
Renders ./views/stylesheet.sass
.
Sass’s options can be set globally through Sinatra’s configurations, see Options and Configurations, and overridden on an individual basis.
set :sass, :style => :compact # default Sass style is :nested
get '/stylesheet.css' do
sass :stylesheet, :style => :expanded # overridden
end
Scss Templates
The haml
or sass
gem/library is required to render Scss templates:
# You'll need to require haml or sass in your app
require 'sass'
get '/stylesheet.css' do
scss :stylesheet
end
Renders ./views/stylesheet.scss
.
Scss’s options can be set globally through Sinatra’s configurations, see Options and Configurations, and overridden on an individual basis.
set :scss, :style => :compact # default Scss style is :nested
get '/stylesheet.css' do
scss :stylesheet, :style => :expanded # overridden
end
Less Templates
The less
gem/library is required to render Less templates:
# You'll need to require less in your app
require 'less'
get '/stylesheet.css' do
less :stylesheet
end
Renders ./views/stylesheet.less
.
Liquid Templates
The liquid
gem/library is required to render Liquid templates:
# You'll need to require liquid in your app
require 'liquid'
get '/' do
liquid :index
end
Renders ./views/index.liquid
.
Since you cannot call Ruby methods (except for yield
) from a Liquid template, you almost always want to pass locals to it:
liquid :index, :locals => { :key => 'value' }
Markdown Templates
The rdiscount
gem/library is required to render Markdown templates:
# You'll need to require rdiscount in your app
require "rdiscount"
get '/' do
markdown :index
end
Renders ./views/index.markdown
(md
and mkd
are also valid file extensions).
It is not possible to call methods from markdown, nor to pass locals to it. You therefore will usually use it in combination with another rendering engine:
erb :overview, :locals => { :text => markdown(:introduction) }
Note that you may also call the markdown
method from within other templates:
%h1 Hello From Haml!
%p= markdown(:greetings)
Since you cannot call Ruby from Markdown, you cannot use layouts written in Markdown. However, it is possible to use another rendering engine for the template than for the layout by passing the :layout_engine
option:
get '/' do
markdown :index, :layout_engine => :erb
end
This will render ./views/index.md
with ./views/layout.erb
as layout.
Remember that you can set such rendering options globally:
set :markdown, :layout_engine => :haml, :layout => :post
get '/' do
markdown :index
end
This will render ./views/index.md
(and any other Markdown template) with ./views/post.haml
as layout.
It is also possible to parse Markdown with BlueCloth rather than RDiscount:
require 'bluecloth'
Tilt.register 'markdown', BlueClothTemplate
Tilt.register 'mkd', BlueClothTemplate
Tilt.register 'md', BlueClothTemplate
get '/' do
markdown :index
end
Renders ./views/index.md
with BlueCloth.
Textile Templates
The RedCloth
gem/library is required to render Textile templates:
# You'll need to require redcloth in your app
require "redcloth"
get '/' do
textile :index
end
Renders ./views/index.textile
.
It is not possible to call methods from textile, nor to pass locals to it. You therefore will usually use it in combination with another rendering engine:
erb :overview, :locals => { :text => textile(:introduction) }
Note that you may also call the textile
method from within other templates:
%h1 Hello From Haml!
%p= textile(:greetings)
Since you cannot call Ruby from Textile, you cannot use layouts written in Textile. However, it is possible to use another rendering engine for the template than for the layout by passing the :layout_engine
option:
get '/' do
textile :index, :layout_engine => :erb
end
This will render ./views/index.textile
with ./views/layout.erb
as layout.
Remember that you can set such rendering options globally:
set :textile, :layout_engine => :haml, :layout => :post
get '/' do
textile :index
end
This will render ./views/index.textile
(and any other Textile template) with ./views/post.haml
as layout.
RDoc Templates
The rdoc
gem/library is required to render RDoc templates:
# You'll need to require rdoc/markup/to_html in your app
require "rdoc/markup/to_html"
get '/' do
rdoc :index
end
Renders ./views/index.rdoc
.
It is not possible to call methods from rdoc, nor to pass locals to it. You therefore will usually use it in combination with another rendering engine:
erb :overview, :locals => { :text => rdoc(:introduction) }
Note that you may also call the rdoc
method from within other templates:
%h1 Hello From Haml!
%p= rdoc(:greetings)
Since you cannot call Ruby from RDoc, you cannot use layouts written in RDoc. However, it is possible to use another rendering engine for the template than for the layout by passing the :layout_engine
option:
get '/' do
rdoc :index, :layout_engine => :erb
end
This will render ./views/index.rdoc
with ./views/layout.erb
as layout.
Remember that you can set such rendering options globally:
set :rdoc, :layout_engine => :haml, :layout => :post
get '/' do
rdoc :index
end
This will render ./views/index.rdoc
(and any other RDoc template) with ./views/post.haml
as layout.
Radius Templates
The radius
gem/library is required to render Radius templates:
# You'll need to require radius in your app
require 'radius'
get '/' do
radius :index
end
Renders ./views/index.radius
.
Since you cannot call Ruby methods (except for yield
) from a Radius template, you almost always want to pass locals to it:
radius :index, :locals => { :key => 'value' }
Markaby Templates
The markaby
gem/library is required to render Markaby templates:
# You'll need to require markaby in your app
require 'markaby'
get '/' do
markaby :index
end
Renders ./views/index.mab
.
You may also use inline Markaby:
get '/' do
markaby { h1 "Welcome!" }
end
Slim Templates
The slim
gem/library is required to render Slim templates:
# You'll need to require slim in your app
require 'slim'
get '/' do
slim :index
end
Renders ./views/index.slim
.
CoffeeScript Templates
The coffee-script
gem/library and at least one of the following options to execute JavaScript:
-
node
(from Node.js) in your path -
you must be running on OSX
-
therubyracer
gem/library
See github.com/josh/ruby-coffee-script for an updated list of options.
Now you can render CoffeeScript templates:
# You'll need to require coffee-script in your app
require 'coffee-script'
get '/application.js' do
coffee :application
end
Renders ./views/application.coffee
.
Embedded Templates
get '/' do
haml '%div.title Hello World'
end
Renders the embedded template string.
Accessing Variables in Templates
Templates are evaluated within the same context as route handlers. Instance variables set in route handlers are directly accessible by templates:
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.
Inline Templates
Templates may be defined at the end of the source file:
require 'sinatra'
get '/' do
haml :index
end
__END__
NOTE: Inline templates defined in the source file that requires sinatra are automatically loaded. Call enable :inline_templates
explicitly if you have inline templates in other source files.
Named Templates
Templates may also be defined using the top-level template
method:
template :layout do
"%html\n =yield\n"
end
template :index do
'%div.title Hello World!'
end
get '/' do
haml :index
end
If a template named “layout” exists, it will be used each time a template is rendered. You can individually disable layouts by passing :layout => false
or disable them by default via set :haml, :layout => false
:
get '/' do
haml :index, :layout => !request.xhr?
end
Associating File Extensions
To associate a file extension with a template engine, use Tilt.register
. For instance, if you like to use the file extension tt
for Textile templates, you can do the following:
Tilt.register :tt, Tilt[:textile]
Adding Your Own Template Engine
First, register your engine with Tilt, then create a rendering method:
Tilt.register :myat, MyAwesomeTemplateEngine
helpers do
def myat(*args) render(:myat, *args) end
end
get '/' do
myat :index
end
Renders ./views/index.myat
. See github.com/rtomayko/tilt to learn more about Tilt.
Filters
Before filters are evaluated before each request within the same context as the routes will be and can modify the request and response. Instance variables set in filters are accessible by routes and templates:
before do
@note = 'Hi!'
request.path_info = '/foo/bar/baz'
end
get '/foo/*' do
@note #=> 'Hi!'
params[:splat] #=> 'bar/baz'
end
After filters are evaluated after each request within the same context and can also modify the request and response. Instance variables set in before filters and routes are accessible by after filters:
after do
puts response.status
end
Note: Unless you use the body
method rather than just returning a String from the routes, the body will not yet be available in the after filter, since it is generated later on.
Filters optionally take a pattern, causing them to be evaluated only if the request path matches that pattern:
before '/protected/*' do
authenticate!
end
after '/create/:slug' do |slug|
session[:last_slug] = slug
end
Like routes, filters also take conditions:
before :agent => /Songbird/ do
# ...
end
after '/blog/*', :host_name => 'example.com' do
# ...
end
Helpers
Use the top-level helpers
method to define helper methods for use in route handlers and templates:
helpers do
def (name)
"#{name}bar"
end
end
get '/:name' do
(params[:name])
end
Using Sessions
A session is used to keep state during requests. If activated, you have one session hash per user session:
enable :sessions
get '/' do
"value = " << session[:value].inspect
end
get '/:value' do
session[:value] = params[:value]
end
Note that enable :sessions
actually stores all data in a cookie. This might not always be what you want (storing lots of data will increase your traffic, for instance). You can use any Rack session middleware, in order to do so, do not call enable :sessions
, but instead pull in your middleware of choice how you would any other middleware:
use Rack::Session::Pool, :expire_after => 2592000
get '/' do
"value = " << session[:value].inspect
end
get '/:value' do
session[:value] = params[:value]
end
To improve security, the session data in the cookie is signed with a session secret. A random secret is generate for you by Sinatra. However, since this secret will change with every start of your application, you might want to set the secret yourself, so all your application instances share it:
set :session_secret, 'super secret'
Halting
To immediately stop a request within a filter or route use:
halt
You can also specify the status when halting:
halt 410
Or the body:
halt 'this will be the body'
Or both:
halt 401, 'go away!'
With headers:
halt 402, {'Content-Type' => 'text/plain'}, 'revenge'
It is of course possible to combine a template with halt
:
halt erb(:error)
Passing
A route can punt processing to the next matching route using pass
:
get '/guess/:who' do
pass unless params[:who] == 'Frank'
'You got me!'
end
get '/guess/*' do
'You missed!'
end
The route block is immediately exited and control continues with the next matching route. If no matching route is found, a 404 is returned.
Triggering Another Route
Sometimes pass
is not what you want, instead you would like to get the result of calling another route. Simply use call
to achieve this:
get '/foo' do
status, headers, body = call request.env.merge("PATH_INFO" => '/bar')
[status, body.upcase]
end
get '/bar' do
"bar"
end
Note that in the example above, you would ease testing and increase performance by simply moving "bar"
into a helper used by both /foo
and /bar
.
If you want the request to be sent to the same application instance rather than a duplicate, use call!
instead of call
.
Check out the Rack specification if you want to learn more about call
.
Setting Body, Status Code and Headers
It is possible and recommended to set the status code and response body with the return value of the route block. However, in some scenarios you might want to set the body at an arbitrary point in the execution flow. You can do so with the body
helper method. If you do so, you can use that method from there on to access the body:
get '/foo' do
body "bar"
end
after do
puts body
end
It is also possible to pass a block to body
, which will be executed by the Rack handler (this can be used to implement streaming, see “Return Values”).
Similar to the body, you can also set the status code and headers:
get '/foo' do
status 418
headers \
"Allow" => "BREW, POST, GET, PROPFIND, WHEN"
"Refresh" => "Refresh: 20; http://www.ietf.org/rfc/rfc2324.txt"
body "I'm a tea pot!"
end
Like body
, headers
and status
with no arguments can be used to access their current values.
Mime Types
When using send_file
or static files you may have mime types Sinatra doesn’t understand. Use mime_type
to register them by file extension:
mime_type :foo, 'text/foo'
You can also use it with the content_type
helper:
get '/' do
content_type :foo
"foo foo foo"
end
Generating URLs
For generating URLs you should use the url
helper method, for instance, in Haml:
%a{:href => url('/foo')} foo
It takes reverse proxies and Rack routers into account, if present.
This method is also aliased to to
(see below for an example).
Browser Redirect
You can trigger a browser redirect with the redirect
helper method:
get '/foo' do
redirect to('/bar')
end
Any additional parameters are handled like arguments passed to halt
:
redirect to('/bar'), 303
redirect 'http://google.com', 'wrong place, buddy'
You can also easily redirect back to the page the user came from with redirect back
:
get '/foo' do
"<a href='/bar'>do something</a>"
end
get '/bar' do
do_something
redirect back
end
To pass arguments with a redirect, either add them to the query:
redirect to('/bar?sum=42')
Or use a session:
enable :session
get '/foo' do
session[:secret] = 'foo'
redirect to('/bar')
end
get '/bar' do
session[:secret]
end
Cache Control
Setting your headers correctly is the foundation for proper HTTP caching.
You can easily set the Cache-Control header with like this:
get '/' do
cache_control :public
"cache it!"
end
Pro tip: Set up caching in a before filter:
before do
cache_control :public, :must_revalidate, :max_age => 60
end
If you are using the expires
helper to set the corresponding header, Cache-Control
will be set automatically for you:
before do
expires 500, :public, :must_revalidate
end
To properly use caches, you should consider using etag
and last_modified
. It is recommended to call those helpers before doing heavy lifting, as they will immediately flush a response if the client already has the current version in its cache:
get '/article/:id' do
@article = Article.find params[:id]
last_modified @article.updated_at
etag @article.sha1
erb :article
end
It is also possible to use a weak ETag:
etag @article.sha1, :weak
These helpers will not do any caching for you, but rather feed the necessary information to your cache. If you are looking for a quick caching solutions, try rack-cache:
require "rack/cache"
require "sinatra"
use Rack::Cache
get '/' do
cache_control :public, :max_age => 36000
sleep 5
"hello"
end
Sending Files
For sending files, you can use the send_file
helper method:
get '/' do
send_file 'foo.png'
end
It also takes a couple of options:
send_file 'foo.png', :type => :jpg
The options are:
- filename
-
file name, in response, defaults to the real file name.
- last_modified
-
value for Last-Modified header, defaults to the file’s mtime.
- type
-
content type to use, guessed from the file extension if missing.
- disposition
-
used for Content-Disposition, possible values:
nil
(default),:attachment
and:inline
- length
-
Content-Length header, defaults to file size.
If supported by the Rack handler, other means than streaming from the Ruby process will be used. If you use this helper method, Sinatra will automatically handle range requests.
Accessing the Request Object
The incoming request object can be accessed from request level (filter, routes, error handlers) through the request
method:
# app running on http://example.com/example
get '/foo' do
request.body # request body sent by the client (see below)
request.scheme # "http"
request.script_name # "/example"
request.path_info # "/foo"
request.port # 80
request.request_method # "GET"
request.query_string # ""
request.content_length # length of request.body
request.media_type # media type of request.body
request.host # "example.com"
request.get? # true (similar methods for other verbs)
request.form_data? # false
request["SOME_HEADER"] # value of SOME_HEADER header
request.referrer # the referrer of the client or '/'
request.user_agent # user agent (used by :agent condition)
request. # hash of browser cookies
request.xhr? # is this an ajax request?
request.url # "http://example.com/example/foo"
request.path # "/example/foo"
request.ip # client IP address
request.secure? # false (would be true over ssl)
request.forwarded? # true (if running behind a reverse proxy)
request.env # raw env hash handed in by Rack
end
Some options, like script_name
or path_info
, can also be written:
before { request.path_info = "/" }
get "/" do
"all requests end up here"
end
The request.body
is an IO or StringIO object:
post "/api" do
request.body.rewind # in case someone already read it
data = JSON.parse request.body.read
"Hello #{data['name']}!"
end
Attachments
You can use the attachment
helper to tell the browser the response should be stored on disk rather than displayed in the browser:
get '/' do
"store it!"
end
You can also pass it a file name:
get '/' do
"info.txt"
"store it!"
end
Looking Up Template Files
The find_template
helper is used to find template files for rendering:
find_template settings.views, 'foo', Tilt[:haml] do |file|
puts "could be #{file}"
end
This is not really useful. But it is useful that you can actually override this method to hook in your own lookup mechanism. For instance, if you want to be able to use more than one view directory:
set :views, ['views', 'templates']
helpers do
def find_template(views, name, engine, &block)
Array(views).each { |v| super(v, name, engine, &block) }
end
end
Another example would be using different directories for different engines:
set :views, :sass => 'views/sass', :haml => 'templates', :default => 'views'
helpers do
def find_template(views, name, engine, &block)
_, folder = views.detect { |k,v| engine == Tilt[k] }
folder ||= views[:default]
super(folder, name, engine, &block)
end
end
You can also easily wrap this up in an extension and share with others!
Note that find_template
does not check if the file really exists but rather calls the given block for all possible paths. This is not a performance issue, since render
will use break
as soon as a file is found. Also, template locations (and content) will be cached if you are not running in development mode. You should keep that in mind if you write a really crazy method.
Configuration
Run once, at startup, in any environment:
configure do
# setting one option
set :option, 'value'
# setting multiple options
set :a => 1, :b => 2
# same as `set :option, true`
enable :option
# same as `set :option, false`
disable :option
# you can also have dynamic settings with blocks
set(:css_dir) { File.join(views, 'css') }
end
Run only when the environment (RACK_ENV environment variable) is set to :production
:
configure :production do
...
end
Run when the environment is set to either :production
or :test
:
configure :production, :test do
...
end
You can access those options via settings
:
configure do
set :foo, 'bar'
end
get '/' do
settings.foo? # => true
settings.foo # => 'bar'
...
end
Available Settings
- absolute_redirects
-
If disabled, Sinatra will allow relative redirects, however, Sinatra will no longer conform with RFC 2616 (HTTP 1.1), which only allows absolute redirects.
Enable if your app is running behind a reverse proxy that has not been set up properly. Note that the
url
helper will still produce absolute URLs, unless you pass infalse
as second parameter.Disabled per default.
- add_charsets
-
mime types the
content_type
helper will automatically add the charset info to.You should add to it rather than overriding this option:
settings.add_charsets << "application/foobar"
- app_file
-
main application file, used to detect project root, views and public folder and inline templates.
- bind
-
IP address to bind to (default: 0.0.0.0). Only used for built-in server.
- default_encoding
-
encoding to assume if unknown (defaults to
"utf-8"
). - dump_errors
-
display errors in the log.
- environment
-
current environment, defaults to
ENV['RACK_ENV']
, or"development"
if not available. - logging
-
use the logger.
- lock
-
Places a lock around every request, only running processing on request per Ruby process concurrently.
Enabled if your app is not thread-safe. Disabled per default.
- method_override
-
use
_method
magic to allow put/delete forms in browsers that don’t support it. - port
-
Port to listen on. Only used for built-in server.
- prefixed_redirects
-
Whether or not to insert
request.script_name
into redirects if no absolute path is given. That wayredirect '/foo'
would behave likeredirect to('/foo')
. Disabled per default. - public
-
folder public files are served from
- reload_templates
-
whether or not to reload templates between requests. Enabled in development mode and on Ruby 1.8.6 (to compensate a bug in Ruby causing a memory leak).
- root
-
project root folder.
- raise_errors
-
raise exceptions (will stop application).
- run
-
if enabled, Sinatra will handle starting the web server, do not enable if using rackup or other means.
- running
-
is the built-in server running now? do not change this setting!
- server
-
server or list of servers to use for built-in server. defaults to [‘thin’, ‘mongrel’, ‘webrick’], order indicates priority.
- sessions
-
enable cookie based sessions.
- show_exceptions
-
show a stack trace in the browser.
- static
-
Whether Sinatra should handle serving static files. Disable when using a Server able to do this on its own. Disabling will boost performance. Enabled per default.
- views
-
views folder.
Error Handling
Error handlers run within the same context as routes and before filters, which means you get all the goodies it has to offer, like haml
, erb
, halt
, etc.
Not Found
When a Sinatra::NotFound
exception is raised, or the response’s status code is 404, the not_found
handler is invoked:
not_found do
'This is nowhere to be found.'
end
Error
The error
handler is invoked any time an exception is raised from a route block or a filter. The exception object can be obtained from the sinatra.error
Rack variable:
error do
'Sorry there was a nasty error - ' + env['sinatra.error'].name
end
Custom errors:
error MyCustomError do
'So what happened was...' + request.env['sinatra.error'].
end
Then, if this happens:
get '/' do
raise MyCustomError, 'something bad'
end
You get this:
So what happened was... something bad
Alternatively, you can install an error handler for a status code:
error 403 do
'Access forbidden'
end
get '/secret' do
403
end
Or a range:
error 400..510 do
'Boom'
end
Sinatra installs special not_found
and error
handlers when running under the development environment.
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 these components automatically based on configuration so you typically don’t have to use
them explicitly.
Testing
Sinatra tests can be written using any Rack-based testing library or framework. Rack::Test is recommended:
require 'my_sinatra_app'
require 'test/unit'
require 'rack/test'
class MyAppTest < Test::Unit::TestCase
include Rack::Test::Methods
def app
Sinatra::Application
end
def test_my_default
get '/'
assert_equal 'Hello World!', last_response.body
end
def test_with_params
get '/meet', :name => 'Frank'
assert_equal 'Hello Frank!', last_response.body
end
def test_with_rack_env
get '/', {}, 'HTTP_USER_AGENT' => 'Songbird'
assert_equal "You're using Songbird!", last_response.body
end
end
NOTE: The built-in Sinatra::Test module and Sinatra::TestHarness class are deprecated as of the 0.9.2 release.
Sinatra::Base - Middleware, Libraries, and Modular Apps
Defining your app at the top-level works well for micro-apps but has considerable drawbacks when building reusable components such as Rack middleware, Rails metal, simple libraries with a server component, or even Sinatra extensions. The top-level DSL pollutes the Object namespace and assumes a micro-app style configuration (e.g., a single application file, ./public and ./views directories, logging, exception detail page, etc.). That’s where Sinatra::Base comes into play:
require 'sinatra/base'
class MyApp < Sinatra::Base
set :sessions, true
set :foo, 'bar'
get '/' do
'Hello world!'
end
end
The methods available to Sinatra::Base subclasses are exactly as those available via the top-level DSL. Most top-level apps can be converted to Sinatra::Base components with two modifications:
-
Your file should require
sinatra/base
instead ofsinatra
; otherwise, all of Sinatra’s DSL methods are imported into the main namespace. -
Put your app’s routes, error handlers, filters, and options in a subclass of Sinatra::Base.
Sinatra::Base
is a blank slate. Most options are disabled by default, including the built-in server. See Options and Configuration for details on available options and their behavior.
Modular vs. Classic Style
Contrary to common belief, there is nothing wrong with classic style. If it suits your application, you do not have to switch to a modular application.
There are only two downsides compared with modular style:
-
You may only have one Sinatra application per Ruby process. If you plan to use more, switch to modular style.
-
Classic style pollutes Object with delegator methods. If you plan to ship your application in a library/gem, switch to modular style.
There is no reason you cannot mix modular and classic style.
If switching from one style to the other, you should be aware of slight differences in the setting:
Setting Classic Modular
app_file file loading sinatra nil
run $0 == app_file false
logging true false
method_override true false
inline_templates true false
Serving a Modular Application
There are two common options for starting a modular app, actively starting with run!
:
# my_app.rb
require 'sinatra/base'
class MyApp < Sinatra::Base
# ... app code here ...
# start the server if ruby file executed directly
run! if app_file == $0
end
Start with:
ruby my_app.rb
Or with a config.ru
, which allows using any Rack handler:
# config.ru
require 'my_app'
run MyApp
Run:
rackup -p 4567
Using a Classic Style Application with a config.ru
Write your app file:
# app.rb
require 'sinatra'
get '/' do
'Hello world!'
end
And a corresponding config.ru
:
require 'app'
run Sinatra::Application
When to use a config.ru?
Good signs you probably want to use a config.ru
:
-
You want to deploy with a different Rack handler (Passenger, Unicorn, Heroku, …).
-
You want to use more than one subclass of
Sinatra::Base
. -
You want to use Sinatra only for middleware, but not as endpoint.
There is no need to switch to a config.ru
only because you switched to modular style, and you don’t have to use modular style for running with a config.ru
.
Using Sinatra as Middleware
Not only is Sinatra able to use other Rack middleware, any Sinatra application can in turn be added in front of any Rack endpoint as middleware itself. This endpoint could be another Sinatra application, or any other Rack-based application (Rails/Ramaze/Camping/…):
require 'sinatra/base'
class LoginScreen < Sinatra::Base
enable :sessions
get('/login') { haml :login }
post('/login') do
if params[:name] = 'admin' and params[:password] = 'admin'
session['user_name'] = params[:name]
else
redirect '/login'
end
end
end
class MyApp < Sinatra::Base
# middleware will run before filters
use LoginScreen
before do
unless session['user_name']
halt "Access denied, please <a href='/login'>login</a>."
end
end
get('/') { "Hello #{session['user_name']}." }
end
Scopes and Binding
The scope you are currently in determines what methods and variables are available.
Application/Class Scope
Every Sinatra application corresponds to a subclass of Sinatra::Base. If you are using the top-level DSL (require 'sinatra'
), then this class is Sinatra::Application, otherwise it is the subclass you created explicitly. At class level you have methods like get
or before
, but you cannot access the request
object or the session
, as there only is a single application class for all requests.
Options created via set
are methods at class level:
class MyApp < Sinatra::Base
# Hey, I'm in the application scope!
set :foo, 42
foo # => 42
get '/foo' do
# Hey, I'm no longer in the application scope!
end
end
You have the application scope binding inside:
-
Your application class body
-
Methods defined by extensions
-
The block passed to
helpers
-
Procs/blocks used as value for
set
You can reach the scope object (the class) like this:
-
Via the object passed to configure blocks (
configure { |c| ... }
) -
settings
from within request scope
Request/Instance Scope
For every incoming request, a new instance of your application class is created and all handler blocks run in that scope. From within this scope you can access the request
and session
object or call rendering methods like erb
or haml
. You can access the application scope from within the request scope via the settings
helper:
class MyApp < Sinatra::Base
# Hey, I'm in the application scope!
get '/define_route/:name' do
# Request scope for '/define_route/:name'
@value = 42
settings.get("/#{params[:name]}") do
# Request scope for "/#{params[:name]}"
@value # => nil (not the same request)
end
"Route defined!"
end
end
You have the request scope binding inside:
-
get/head/post/put/delete/options blocks
-
before/after filters
-
helper methods
-
templates/views
Delegation Scope
The delegation scope just forwards methods to the class scope. However, it does not behave 100% like the class scope, as you do not have the class binding. Only methods explicitly marked for delegation are available and you do not share variables/state with the class scope (read: you have a different self
). You can explicitly add method delegations by calling Sinatra::Delegator.delegate :method_name
.
You have the delegate scope binding inside:
-
The top level binding, if you did
require "sinatra"
-
An object extended with the
Sinatra::Delegator
mixin
Have a look at the code for yourself: here’s the Sinatra::Delegator mixin being included into the main namespace.
Command Line
Sinatra applications can be run directly:
ruby myapp.rb [-h] [-x] [-e ENVIRONMENT] [-p PORT] [-o HOST] [-s HANDLER]
Options are:
-h # help
-p # set the port (default is 4567)
-o # set the host (default is 0.0.0.0)
-e # set the environment (default is development)
-s # specify rack server/handler (default is thin)
-x # turn on the mutex lock (default is off)
Requirements
It is recommended to install Sinatra on Ruby 1.8.7, 1.9.2, JRuby or Rubinius.
The following Ruby versions are officially supported:
- Ruby 1.8.6
-
It is not recommended to use 1.8.6 for Sinatra. However, it will be officially supported until Sinatra 1.3.0 is released. RDoc and CoffeeScript templates are not supported by this Ruby version. 1.8.6 includes a major memory leak in its Hash implementation, which is triggered by Sinatra versions prior to 1.1.1. The current version explicitly prevents this leak at the cost of performance. You will have to downgrade Rack to 1.1.x, as Rack >= 1.2 no longer supports 1.8.6.
- Ruby 1.8.7
-
1.8.7 is fully supported, however, if nothing is keeping you from it, we recommend upgrading to 1.9.2 or switching to JRuby or Rubinius.
- Ruby 1.9.2
-
1.9.2 is supported and recommended. Note that Radius and Markaby are currently not 1.9 compatible. Do not use 1.9.2p0, it is known to cause segmentation faults when using Sinatra.
- Rubinius
-
Rubinius is officially supported (Rubinius >= 1.2.3), everything, including all template languages, works.
- JRuby
-
JRuby is officially supported (JRuby >= 1.6.0). No issues with third party template libraries are known, however, if you choose to use JRuby, please look into JRuby rack handlers, as the Thin web server is not fully supported on JRuby. JRuby’s support for C extensions is still experimental, which only affects RDiscount at the moment.
We also keep an eye on upcoming Ruby versions.
The following Ruby implementations are not officially supported but still are known to run Sinatra:
-
Older versions of JRuby and Rubinius
-
MacRuby, Maglev, IronRuby
-
Ruby 1.9.0 and 1.9.1
Not being officially supported means if things only break there and not on a supported platform, we assume it’s not our issue but theirs.
We also run our CI against ruby-head (the upcoming 1.9.3), but we can’t guarantee anything, since it is constantly moving. Expect 1.9.3p0 to be supported.
Sinatra should work on any operating system supported by the chosen Ruby implementation.
The Bleeding Edge
If you would like to use Sinatra’s latest bleeding code, feel free to run your application against the master branch, it should be rather stable.
We also push out prerelease gems from time to time, so you can do a
gem install sinatra --pre
To get some of the latest features.
With Bundler
If you want to run your application with the latest Sinatra, using Bundler is the recommended way.
First, install bundler, if you haven’t:
gem install bundler
Then, in your project directory, create a Gemfile
:
source :rubygems
gem 'sinatra', :git => "git://github.com/sinatra/sinatra.git"
# other dependencies
gem 'haml' # for instance, if you use haml
gem 'activerecord', '~> 3.0' # maybe you also need ActiveRecord 3.x
Note that you will have to list all your applications dependencies in there. Sinatra’s direct dependencies (Rack and Tilt) will, however, be automatically fetched and added by Bundler.
Now you can run your app like this:
bundle exec ruby myapp.rb
Roll Your Own
Create a local clone and run your app with the sinatra/lib
directory on the $LOAD_PATH
:
cd myapp
git clone git://github.com/sinatra/sinatra.git
ruby -Isinatra/lib myapp.rb
To update the Sinatra sources in the future:
cd myapp/sinatra
git pull
Install Globally
You can build the gem on your own:
git clone git://github.com/sinatra/sinatra.git
cd sinatra
rake sinatra.gemspec
rake install
If you install gems as root, the last step should be
sudo rake install
Versioning
Sinatra follows Semantic Versioning, both SemVer and SemVerTag.
Further Reading
-
Project Website - Additional documentation, news, and links to other resources.
-
Contributing - Find a bug? Need help? Have a patch?