sinatra/sinatra

Name: sinatra

Owner: Sinatra

Description: Classy web-development dressed in a DSL (official / canonical repo)

Created: 2009-01-14 01:27:30.0

Updated: 2018-01-20 09:20:47.0

Pushed: 2018-01-16 12:05:38.0

Homepage: http://www.sinatrarb.com/

Size: 6155

Language: Ruby

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README

Sinatra

Build Status

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

app.rb
ire 'sinatra'

'/' do
ello world!'

Install the gem:

install sinatra

And run with:

 myapp.rb

View at: http://localhost:4567

The code you changed will not take effect until you restart the server. Please restart the server every time you change or use sinatra/reloader.

It is recommended to also run gem install thin, which Sinatra will pick up if available.

Table of Contents
Routes

In Sinatra, a route is an HTTP method paired with a URL-matching pattern. Each route is associated with a block:

'/' do
 show something ..


 '/' do
 create something ..


'/' do
 replace something ..


h '/' do
 modify something ..


te '/' do
 annihilate something ..


ons '/' do
 appease something ..


 '/' do
 affiliate something ..


nk '/' do
 separate something ..

Routes are matched in the order they are defined. The first route that matches the request is invoked.

Routes with trailing slashes are different from the ones without:

'/foo' do
Does not match "GET /foo/"

Route patterns may include named parameters, accessible via the params hash:

'/hello/:name' do
matches "GET /hello/foo" and "GET /hello/bar"
params['name'] is 'foo' or 'bar'
ello #{params['name']}!"

You can also access named parameters via block parameters:

'/hello/:name' do |n|
matches "GET /hello/foo" and "GET /hello/bar"
params['name'] is 'foo' or 'bar'
n stores params['name']
ello #{n}!"

Route patterns may also include splat (or wildcard) parameters, accessible via the params['splat'] array:

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


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

Or with block parameters:

'/download/*.*' do |path, ext|
ath, ext] # => ["path/to/file", "xml"]

Route matching with Regular Expressions:

/\/hello\/([\w]+)/ do
ello, #{params['captures'].first}!"

Or with a block parameter:

%r{/hello/([\w]+)} do |c|
Matches "GET /meta/hello/world", "GET /hello/world/1234" etc.
ello, #{c}!"

Route patterns may have optional parameters:

'/posts/:format?' do
matches "GET /posts/" and any extension "GET /posts/json", "GET /posts/xml" etc

Routes may also utilize query parameters:

'/posts' do
matches "GET /posts?title=foo&author=bar"
tle = params['title']
thor = params['author']
uses title and author variables; query is optional to the /posts route

By the way, unless you disable the path traversal attack protection (see below), the request path might be modified before matching against your routes.

You may customize the Mustermann options used for a given route by passing in a :mustermann_opts hash:

'\A/posts\z', :mustermann_opts => { :type => :regexp, :check_anchors => false } do
matches /posts exactly, with explicit anchoring
f you match an anchored pattern clap your hands!"

It looks like a condition, but it isn't one! These options will be merged into the global :mustermann_opts hash described below.

Conditions

Routes may include a variety of matching conditions, such as the user agent:

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


'/foo' do
Matches non-songbird browsers

Other available conditions are host_name and provides:

'/', :host_name => /^admin\./ do
dmin Area, Access denied!"


'/', :provides => 'html' do
ml :index


'/', :provides => ['rss', 'atom', 'xml'] do
ilder :feed

provides searches the request's Accept header.

You can easily define your own conditions:

:probability) { |value| condition { rand <= value } }

'/win_a_car', :probability => 0.1 do
ou won!"


'/win_a_car' do
orry, you lost."

For a condition that takes multiple values use a splat:

:auth) do |*roles|   # <- notice the splat here
ndition do
unless logged_in? && roles.any? {|role| current_user.in_role? role }
  redirect "/login/", 303
end
d


"/my/account/", :auth => [:user, :admin] do
our Account Details"


"/only/admin/", :auth => :admin do
nly admins are allowed here!"
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:

That way we can, for instance, easily implement a streaming example:

s Stream
f each
100.times { |i| yield "#{i}\n" }
d


'/') { Stream.new }

You can also use the stream helper method (described below) to reduce boiler plate and embed the streaming logic in the route.

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:

s AllButPattern
tch = Struct.new(:captures)

f initialize(except)
@except   = except
@captures = Match.new([])
d

f match(str)
@captures unless @except === str
d


all_but(pattern)
lButPattern.new(pattern)


all_but("/index") do
...

Note that the above example might be over-engineered, as it can also be expressed as:

// do
ss if request.path_info == "/index"
...

Or, using negative look ahead:

%r{(?!/index)} do
...
Static Files

Static files are served from the ./public directory. You can specify a different location by setting the :public_folder option:

:public_folder, 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.

Use the :static_cache_control setting (see below) to add Cache-Control header info.

Views / Templates

Each template language is exposed via its own rendering method. These methods simply return a string:

'/' do
b :index

This renders views/index.erb.

Instead of a template name, you can also just pass in the template content directly:

'/' do
de = "<%= Time.now %>"
b code

Templates take a second argument, the options hash:

'/' do
b :index, :layout => :post

This will render views/index.erb embedded in the views/post.erb (default is views/layout.erb, if it exists).

Any options not understood by Sinatra will be passed on to the template engine:

'/' do
ml :index, :format => :html5

You can also set options per template language in general:

:haml, :format => :html5

'/' do
ml :index

Options passed to the render method override options set via set.

Available Options:

locals
List of locals passed to the document. Handy with partials. Example: erb "<%= foo %>", :locals => {:foo => "bar"}
default_encoding
String encoding to use if uncertain. Defaults to settings.default_encoding.
views
Views folder to load templates from. Defaults to settings.views.
layout
Whether to use a layout (true or false). If it's a Symbol, specifies what template to use. Example: erb :index, :layout => !request.xhr?
content_type
Content-Type the template produces. Default depends on template language.
scope
Scope to render template under. Defaults to the application instance. If you change this, instance variables and helper methods will not be available.
layout_engine
Template engine to use for rendering the layout. Useful for languages that do not support layouts otherwise. Defaults to the engine used for the template. Example: set :rdoc, :layout_engine => :erb
layout_options
Special options only used for rendering the layout. Example: set :rdoc, :layout_options => { :views => 'views/layouts' }

Templates are assumed to be located directly under the ./views directory. To use a different views directory:

:views, settings.root + '/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' or 'subdir/template'.to_sym). You must use a symbol because otherwise rendering methods will render any strings passed to them directly.

Literal Templates
'/' do
ml '%div.title Hello World'

Renders the template string. You can optionally specify :path and :line for a clearer backtrace if there is a filesystem path or line associated with that string:

'/' do
ml '%div.title Hello World', :path => 'examples/file.haml', :line => 3
Available Template Languages

Some languages have multiple implementations. To specify what implementation to use (and to be thread-safe), you should simply require it first:

ire 'rdiscount' # or require 'bluecloth'
'/') { markdown :index }
Haml Templates
Dependency haml
File Extension .haml
Example haml :index, :format => :html5
Erb Templates
Dependency erubis or erb (included in Ruby)
File Extensions .erb, .rhtml or .erubis (Erubis only)
Example erb :index
Builder Templates
Dependency builder
File Extension .builder
Example builder { |xml| xml.em "hi" }

It also takes a block for inline templates (see example).

Nokogiri Templates
Dependency nokogiri
File Extension .nokogiri
Example nokogiri { |xml| xml.em "hi" }

It also takes a block for inline templates (see example).

Sass Templates
Dependency sass
File Extension .sass
Example sass :stylesheet, :style => :expanded
SCSS Templates
Dependency sass
File Extension .scss
Example scss :stylesheet, :style => :expanded
Less Templates
Dependency less
File Extension .less
Example less :stylesheet
Liquid Templates
Dependency liquid
File Extension .liquid
Example liquid :index, :locals => { :key => 'value' }

Since you cannot call Ruby methods (except for yield) from a Liquid template, you almost always want to pass locals to it.

Markdown Templates
Dependency Anyone of: RDiscount, RedCarpet, BlueCloth, kramdown, maruku
File Extensions .markdown, .mkd and .md
Example markdown :index, :layout_engine => :erb

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:

:overview, :locals => { :text => markdown(:introduction) }

Note that you may also call the markdown method from within other templates:

Hello From Haml!
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.

Textile Templates
Dependency RedCloth
File Extension .textile
Example textile :index, :layout_engine => :erb

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:

:overview, :locals => { :text => textile(:introduction) }

Note that you may also call the textile method from within other templates:

Hello From Haml!
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.

RDoc Templates
Dependency RDoc
File Extension .rdoc
Example rdoc :README, :layout_engine => :erb

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:

:overview, :locals => { :text => rdoc(:introduction) }

Note that you may also call the rdoc method from within other templates:

Hello From Haml!
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.

AsciiDoc Templates
Dependency Asciidoctor
File Extension .asciidoc, .adoc and .ad
Example asciidoc :README, :layout_engine => :erb

Since you cannot call Ruby methods directly from an AsciiDoc template, you almost always want to pass locals to it.

Radius Templates
Dependency Radius
File Extension .radius
Example radius :index, :locals => { :key => 'value' }

Since you cannot call Ruby methods directly from a Radius template, you almost always want to pass locals to it.

Markaby Templates
Dependency Markaby
File Extension .mab
Example markaby { h1 "Welcome!" }

It also takes a block for inline templates (see example).

RABL Templates
Dependency Rabl
File Extension .rabl
Example rabl :index
Slim Templates
Dependency Slim Lang
File Extension .slim
Example slim :index
Creole Templates
Dependency Creole
File Extension .creole
Example creole :wiki, :layout_engine => :erb

It is not possible to call methods from Creole, nor to pass locals to it. You therefore will usually use it in combination with another rendering engine:

:overview, :locals => { :text => creole(:introduction) }

Note that you may also call the creole method from within other templates:

Hello From Haml!
creole(:greetings)

Since you cannot call Ruby from Creole, you cannot use layouts written in Creole. However, it is possible to use another rendering engine for the template than for the layout by passing the :layout_engine option.

MediaWiki Templates
Dependency WikiCloth
File Extension .mediawiki and .mw
Example mediawiki :wiki, :layout_engine => :erb

It is not possible to call methods from MediaWiki markup, nor to pass locals to it. You therefore will usually use it in combination with another rendering engine:

:overview, :locals => { :text => mediawiki(:introduction) }

Note that you may also call the mediawiki method from within other templates:

Hello From Haml!
mediawiki(:greetings)

Since you cannot call Ruby from MediaWiki, you cannot use layouts written in MediaWiki. However, it is possible to use another rendering engine for the template than for the layout by passing the :layout_engine option.

CoffeeScript Templates
Dependency CoffeeScript and a way to execute javascript
File Extension .coffee
Example coffee :index
Stylus Templates
Dependency Stylus and a way to execute javascript
File Extension .styl
Example stylus :index

Before being able to use Stylus templates, you need to load stylus and stylus/tilt first:

ire 'sinatra'
ire 'stylus'
ire 'stylus/tilt'

'/' do
ylus :example
Yajl Templates
Dependency yajl-ruby
File Extension .yajl
Example yajl :index, :locals => { :key => 'qux' }, :callback => 'present', :variable => 'resource'

The template source is evaluated as a Ruby string, and the resulting json variable is converted using #to_json:

 = { :foo => 'bar' }
[:baz] = key

The :callback and :variable options can be used to decorate the rendered object:

resource = {"foo":"bar","baz":"qux"};
ent(resource);
WLang Templates
Dependency WLang
File Extension .wlang
Example wlang :index, :locals => { :key => 'value' }

Since calling ruby methods is not idiomatic in WLang, you almost always want to pass locals to it. Layouts written in WLang and yield are supported, though.

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:

'/:id' do
oo = Foo.find(params['id'])
ml '%h1= @foo.name'

Or, specify an explicit Hash of local variables:

'/:id' do
o = Foo.find(params['id'])
ml '%h1= bar.name', :locals => { :bar => foo }

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

Templates with yield and nested layouts

A layout is usually just a template that calls yield. Such a template can be used either through the :template option as described above, or it can be rendered with a block as follows:

:post, :layout => false do
b :index

This code is mostly equivalent to erb :index, :layout => :post.

Passing blocks to rendering methods is most useful for creating nested layouts:

:main_layout, :layout => false do
b :admin_layout do
erb :user
d

This can also be done in fewer lines of code with:

:admin_layout, :layout => :main_layout do
b :user

Currently, the following rendering methods accept a block: erb, haml, liquid, slim, wlang. Also the general render method accepts a block.

Inline Templates

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

ire 'sinatra'

'/' do
ml :index


D__

ayout
l
yield

ndex
.title Hello world.

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:

late :layout do
html\n  =yield\n"


late :index do
div.title Hello World!'


'/' do
ml :index

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:

'/' do
ml :index, :layout => !request.xhr?
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:

.register :tt, Tilt[:textile]
Adding Your Own Template Engine

First, register your engine with Tilt, then create a rendering method:

.register :myat, MyAwesomeTemplateEngine

ers do
f myat(*args) render(:myat, *args) end


'/' do
at :index

Renders ./views/index.myat. Learn more about Tilt.

Using Custom Logic for Template Lookup

To implement your own template lookup mechanism you can write your own #find_template method:

igure do
t :views [ './views/a', './views/b' ]


find_template(views, name, engine, &block)
ray(views).each do |v|
super(v, name, engine, &block)
d
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:

re do
ote = 'Hi!'
quest.path_info = '/foo/bar/baz'


'/foo/*' do
ote #=> 'Hi!'
rams['splat'] #=> 'bar/baz'

After filters are evaluated after each request within the same context as the routes will be and can also modify the request and response. Instance variables set in before filters and routes are accessible by after filters:

r do
ts response.status

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:

re '/protected/*' do
thenticate!


r '/create/:slug' do |slug|
ssion[:last_slug] = slug

Like routes, filters also take conditions:

re :agent => /Songbird/ do
...


r '/blog/*', :host_name => 'example.com' do
...
Helpers

Use the top-level helpers method to define helper methods for use in route handlers and templates:

ers do
f bar(name)
"#{name}bar"
d


'/:name' do
r(params['name'])

Alternatively, helper methods can be separately defined in a module:

le FooUtils
f foo(name) "#{name}foo" end


le BarUtils
f bar(name) "#{name}bar" end


ers FooUtils, BarUtils

The effect is the same as including the modules in the application class.

Using Sessions

A session is used to keep state during requests. If activated, you have one session hash per user session:

le :sessions

'/' do
alue = " << session[:value].inspect


'/:value' do
ssion['value'] = params['value']
Session Secret Security

To improve security, the session data in the cookie is signed with a session secret using HMAC-SHA1. This session secret should optimally be a cryptographically secure random value of an appropriate length which for HMAC-SHA1 is greater than or equal to 64 bytes (512 bits, 128 hex characters). You would be advised not to use a secret that is less than 32 bytes of randomness (256 bits, 64 hex characters). It is therefore very important that you don't just make the secret up, but instead use a secure random number generator to create it. Humans are extremely bad at generating random values.

By default, a 32 byte secure random session secret is generated for you by Sinatra, but it will change with every restart of your application. If you have multiple instances of your application, and you let Sinatra generate the key, each instance would then have a different session key which is probably not what you want.

For better security and usability it's recommended that you generate a secure random secret and store it in an environment variable on each host running your application so that all of your application instances will share the same secret. You should periodically rotate this session secret to a new value. Here are some examples of how you might create a 64 byte secret and set it:

Session Secret Generation

by -e "require 'securerandom'; puts SecureRandom.hex(64)"
8af...snip...ec0f262ac

Session Secret Generation (Bonus Points)

Use the sysrandom gem to prefer use of system RNG facilities to generate random values instead of userspace OpenSSL which MRI Ruby currently defaults to:

m install sysrandom
ding native extensions.  This could take a while...
essfully installed sysrandom-1.x
m installed

by -e "require 'sysrandom/securerandom'; puts SecureRandom.hex(64)"
8af...snip...ec0f262ac

Session Secret Environment Variable

Set a SESSION_SECRET environment variable for Sinatra to the value you generated. Make this value persistent across reboots of your host. Since the method for doing this will vary across systems this is for illustrative purposes only:

ho "export SESSION_SECRET=99ae8af...snip...ec0f262ac" >> ~/.bashrc

Session Secret App Config

Setup your app config to fail-safe to a secure random secret if the SESSION_SECRET environment variable is not available.

For bonus points use the sysrandom gem here as well:

ire 'securerandom'
r- require 'sysrandom/securerandom'
:session_secret, ENV.fetch('SESSION_SECRET') { SecureRandom.hex(64) }
Session Config

If you want to configure it further, you may also store a hash with options in the sessions setting:

:sessions, :domain => 'foo.com'

To share your session across other apps on subdomains of foo.com, prefix the domain with a . like this instead:

:sessions, :domain => '.foo.com'
Choosing Your Own Session Middleware

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, one of the following methods can be used:

le :sessions
:session_store, Rack::Session::Pool

Or to set up sessions with a hash of options:

:sessions, :expire_after => 2592000
:session_store, Rack::Session::Pool

Another option is to not call enable :sessions, but instead pull in your middleware of choice as you would any other middleware.

It is important to note that when using this method, session based protection will not be enabled by default.

The Rack middleware to do that will also need to be added:

Rack::Session::Pool, :expire_after => 2592000
Rack::Protection::RemoteToken
Rack::Protection::SessionHijacking

See 'Configuring attack protection' for more information.

Halting

To immediately stop a request within a filter or route use:

You can also specify the status when halting:

 410

Or the body:

 'this will be the body'

Or both:

 401, 'go away!'

With headers:

 402, {'Content-Type' => 'text/plain'}, 'revenge'

It is of course possible to combine a template with halt:

 erb(:error)
Passing

A route can punt processing to the next matching route using pass:

'/guess/:who' do
ss unless params['who'] == 'Frank'
ou got me!'


'/guess/*' do
ou missed!'

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:

'/foo' do
atus, headers, body = call env.merge("PATH_INFO" => '/bar')
tatus, headers, body.map(&:upcase)]


'/bar' do
ar"

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:

'/foo' do
dy "bar"


r do
ts body

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:

'/foo' do
atus 418
aders \
"Allow"   => "BREW, POST, GET, PROPFIND, WHEN",
"Refresh" => "Refresh: 20; https://ietf.org/rfc/rfc2324.txt"
dy "I'm a tea pot!"

Like body, headers and status with no arguments can be used to access their current values.

Streaming Responses

Sometimes you want to start sending out data while still generating parts of the response body. In extreme examples, you want to keep sending data until the client closes the connection. You can use the stream helper to avoid creating your own wrapper:

'/' do
ream do |out|
out << "It's gonna be legen -\n"
sleep 0.5
out << " (wait for it) \n"
sleep 1
out << "- dary!\n"
d

This allows you to implement streaming APIs, Server Sent Events, and can be used as the basis for WebSockets. It can also be used to increase throughput if some but not all content depends on a slow resource.

Note that the streaming behavior, especially the number of concurrent requests, highly depends on the web server used to serve the application. Some servers might not even support streaming at all. If the server does not support streaming, the body will be sent all at once after the block passed to stream finishes executing. Streaming does not work at all with Shotgun.

If the optional parameter is set to keep_open, it will not call close on the stream object, allowing you to close it at any later point in the execution flow. This only works on evented servers, like Thin and Rainbows. Other servers will still close the stream:

ng polling

:server, :thin
ections = []

'/subscribe' do
register a client's interest in server events
ream(:keep_open) do |out|
connections << out
# purge dead connections
connections.reject!(&:closed?)
d


 '/:message' do
nnections.each do |out|
# notify client that a new message has arrived
out << params['message'] << "\n"

# indicate client to connect again
out.close
d

acknowledge
essage received"

It's also possible for the client to close the connection when trying to write to the socket. Because of this, it's recommended to check out.closed? before trying to write.

Logging

In the request scope, the logger helper exposes a Logger instance:

'/' do
gger.info "loading data"
...

This logger will automatically take your Rack handler's logging settings into account. If logging is disabled, this method will return a dummy object, so you do not have to worry about it in your routes and filters.

Note that logging is only enabled for Sinatra::Application by default, so if you inherit from Sinatra::Base, you probably want to enable it yourself:

s MyApp < Sinatra::Base
nfigure :production, :development do
enable :logging
d

To avoid any logging middleware to be set up, set the logging setting to nil. However, keep in mind that logger will in that case return nil. A common use case is when you want to set your own logger. Sinatra will use whatever it will find in env['rack.logger'].

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:

igure do
me_type :foo, 'text/foo'

You can also use it with the content_type helper:

'/' do
ntent_type :foo
oo foo foo"
Generating URLs

For generating URLs you should use the url helper method, for instance, in Haml:

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:

'/foo' do
direct to('/bar')

Any additional parameters are handled like arguments passed to halt:

rect to('/bar'), 303
rect 'http://www.google.com/', 'wrong place, buddy'

You can also easily redirect back to the page the user came from with redirect back:

'/foo' do
a href='/bar'>do something</a>"


'/bar' do
_something
direct back

To pass arguments with a redirect, either add them to the query:

rect to('/bar?sum=42')

Or use a session:

le :sessions

'/foo' do
ssion[:secret] = 'foo'
direct to('/bar')


'/bar' do
ssion[:secret]
Cache Control

Setting your headers correctly is the foundation for proper HTTP caching.

You can easily set the Cache-Control header like this:

'/' do
che_control :public
ache it!"

Pro tip: Set up caching in a before filter:

re do
che_control :public, :must_revalidate, :max_age => 60

If you are using the expires helper to set the corresponding header, Cache-Control will be set automatically for you:

re do
pires 500, :public, :must_revalidate

To properly use caches, you should consider using etag or last_modified. It is recommended to call those helpers before doing any heavy lifting, as they will immediately flush a response if the client already has the current version in its cache:

"/article/:id" do
rticle = Article.find params['id']
st_modified @article.updated_at
ag @article.sha1
b :article

It is also possible to use a weak 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 reverse-proxy caching solution, try rack-cache:

ire "rack/cache"
ire "sinatra"

Rack::Cache

'/' do
che_control :public, :max_age => 36000
eep 5
ello"

Use the :static_cache_control setting (see below) to add Cache-Control header info to static files.

According to RFC 2616, your application should behave differently if the If-Match or If-None-Match header is set to *, depending on whether the resource requested is already in existence. Sinatra assumes resources for safe (like get) and idempotent (like put) requests are already in existence, whereas other resources (for instance post requests) are treated as new resources. You can change this behavior by passing in a :new_resource option:

'/create' do
ag '', :new_resource => true
ticle.create
b :new_article

If you still want to use a weak ETag, pass in a :kind option:

 '', :new_resource => true, :kind => :weak
Sending Files

To return the contents of a file as the response, you can use the send_file helper method:

'/' do
nd_file 'foo.png'

It also takes options:

_file 'foo.png', :type => :jpg

The options are:

filename
File name to be used in the response, defaults to the real file name.
last_modified
Value for Last-Modified header, defaults to the file's mtime.
type
Value for Content-Type header, guessed from the file extension if missing.
disposition
Value for Content-Disposition header, possible values: nil (default), :attachment and :inline
length
Value for Content-Length header, defaults to file size.
status
Status code to be sent. Useful when sending a static file as an error page. 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:

p running on http://example.com/example
'/foo' do
= %w[text/css text/html application/javascript]
quest.accept              # ['text/html', '*/*']
quest.accept? 'text/xml'  # true
quest.preferred_type(t)   # 'text/html'
quest.body                # request body sent by the client (see below)
quest.scheme              # "http"
quest.script_name         # "/example"
quest.path_info           # "/foo"
quest.port                # 80
quest.request_method      # "GET"
quest.query_string        # ""
quest.content_length      # length of request.body
quest.media_type          # media type of request.body
quest.host                # "example.com"
quest.get?                # true (similar methods for other verbs)
quest.form_data?          # false
quest["some_param"]       # value of some_param parameter. [] is a shortcut to the params hash.
quest.referrer            # the referrer of the client or '/'
quest.user_agent          # user agent (used by :agent condition)
quest.cookies             # hash of browser cookies
quest.xhr?                # is this an ajax request?
quest.url                 # "http://example.com/example/foo"
quest.path                # "/example/foo"
quest.ip                  # client IP address
quest.secure?             # false (would be true over ssl)
quest.forwarded?          # true (if running behind a reverse proxy)
quest.env                 # raw env hash handed in by Rack

Some options, like script_name or path_info, can also be written:

re { request.path_info = "/" }

"/" do
ll requests end up here"

The request.body is an IO or StringIO object:

 "/api" do
quest.body.rewind  # in case someone already read it
ta = JSON.parse request.body.read
ello #{data['name']}!"
Attachments

You can use the attachment helper to tell the browser the response should be stored on disk rather than displayed in the browser:

'/' do
tachment
tore it!"

You can also pass it a file name:

'/' do
tachment "info.txt"
tore it!"
Dealing with Date and Time

Sinatra offers a time_for helper method that generates a Time object from the given value. It is also able to convert DateTime, Date and similar classes:

'/' do
ss if Time.now > time_for('Dec 23, 2016')
till time"

This method is used internally by expires, last_modified and akin. You can therefore easily extend the behavior of those methods by overriding time_for in your application:

ers do
f time_for(value)
case value
when :yesterday then Time.now - 24*60*60
when :tomorrow  then Time.now + 24*60*60
else super
end
d


'/' do
st_modified :yesterday
pires :tomorrow
ello"
Looking Up Template Files

The find_template helper is used to find template files for rendering:

_template settings.views, 'foo', Tilt[:haml] do |file|
ts "could be #{file}"

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:

:views, ['views', 'templates']

ers do
f find_template(views, name, engine, &block)
Array(views).each { |v| super(v, name, engine, &block) }
d

Another example would be using different directories for different engines:

:views, :sass => 'views/sass', :haml => 'templates', :default => 'views'

ers do
f find_template(views, name, engine, &block)
_, folder = views.detect { |k,v| engine == Tilt[k] }
folder ||= views[:default]
super(folder, name, engine, &block)
d

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:

igure do
setting one option
t :option, 'value'

setting multiple options
t :a => 1, :b => 2

same as `set :option, true`
able :option

same as `set :option, false`
sable :option

you can also have dynamic settings with blocks
t(:css_dir) { File.join(views, 'css') }

Run only when the environment (APP_ENV environment variable) is set to :production:

igure :production do
.

Run when the environment is set to either :production or :test:

igure :production, :test do
.

You can access those options via settings:

igure do
t :foo, 'bar'


'/' do
ttings.foo? # => true
ttings.foo  # => 'bar'
.
Configuring attack protection

Sinatra is using Rack::Protection to defend your application against common, opportunistic attacks. You can easily disable this behavior (which will open up your application to tons of common vulnerabilities):

ble :protection

To skip a single defense layer, set protection to an options hash:

:protection, :except => :path_traversal

You can also hand in an array in order to disable a list of protections:

:protection, :except => [:path_traversal, :session_hijacking]

By default, Sinatra will only set up session based protection if :sessions have been enabled. See 'Using Sessions'. Sometimes you may want to set up sessions “outside” of the Sinatra app, such as in the config.ru or with a separate Rack::Builder instance. In that case you can still set up session based protection by passing the :session option:

:protection, :session => true
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 in false as the second parameter.
Disabled by default.
add_charset
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_charset << "application/foobar"
app_file
Path to the 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 or localhost if your `environment` is set to development). 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['APP_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 by default.
method_override
Use _method magic to allow put/delete forms in browsers that don't support it.
mustermann_opts
A default hash of options to pass to Mustermann.new when compiling routing paths.
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 way redirect '/foo' would behave like redirect to('/foo'). Disabled by default.
protection
Whether or not to enable web attack protections. See protection section above.
public_dir
Alias for public_folder. See below.
public_folder
Path to the folder public files are served from. Only used if static file serving is enabled (see static setting below). Inferred from app_file setting if not set.
quiet
Disables logs generated by Sinatra's start and stop commands. false by default.
reload_templates
Whether or not to reload templates between requests. Enabled in development mode.
root
Path to project root folder. Inferred from app_file setting if not set.
raise_errors
Raise exceptions (will stop application). Enabled by default when environment is set to "test", disabled otherwise.
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. Order indicates priority, default depends on Ruby implementation.
server_settings
If you are using a WEBrick web server, presumably for your development environment, you can pass a hash of options to server_settings, such as SSLEnable or SSLVerifyClient. However, web servers such as Puma and Thin do not support this, so you can set server_settings by defining it as a method when you call configure.
sessions
Enable cookie-based sessions support using Rack::Session::Cookie. See 'Using Sessions' section for more information.
session_store
The Rack session middleware used. Defaults to Rack::Session::Cookie. See 'Using Sessions' section for more information.
show_exceptions
Show a stack trace in the browser when an exception happens. Enabled by default when environment is set to "development", disabled otherwise.
Can also be set to :after_handler to trigger app-specified error handling before showing 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 by default in classic style, disabled for modular apps.
static_cache_control
When Sinatra is serving static files, set this to add Cache-Control headers to the responses. Uses the cache_control helper. Disabled by default.
Use an explicit array when setting multiple values: set :static_cache_control, [:public, :max_age => 300]
threaded
If set to true, will tell Thin to use EventMachine.defer for processing the request.
traps
Whether Sinatra should handle system signals.
views
Path to the views folder. Inferred from app_file setting if not set.
x_cascade
Whether or not to set the X-Cascade header if no route matches. Defaults to true.
Environments

There are three predefined environments: "development", "production" and "test". Environments can be set through the APP_ENV environment variable. The default value is "development". In the "development" environment all templates are reloaded between requests, and special not_found and error handlers display stack traces in your browser. In the "production" and "test" environments, templates are cached by default.

To run different environments, set the APP_ENV environment variable:

ENV=production ruby my_app.rb

You can use predefined methods: development?, test? and production? to check the current environment setting:

'/' do
 settings.development?
"development!"
se
"not development!"
d
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:

found do
his is nowhere to be found.'
Error

The error handler is invoked any time an exception is raised from a route block or a filter. But note in development it will only run if you set the show exceptions option to :after_handler:

:show_exceptions, :after_handler

The exception object can be obtained from the sinatra.error Rack variable:

r do
orry there was a nasty error - ' + env['sinatra.error'].message

Custom errors:

r MyCustomError do
o what happened was...' + env['sinatra.error'].message

Then, if this happens:

'/' do
ise MyCustomError, 'something bad'

You get this:

hat happened was... something bad

Alternatively, you can install an error handler for a status code:

r 403 do
ccess forbidden'


'/secret' do
3

Or a range:

r 400..510 do
oom'

Sinatra installs special not_found and error handlers when running under the development environment to display nice stack traces and additional debugging information in your browser.

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:

ire 'sinatra'
ire 'my_custom_middleware'

Rack::Lint
MyCustomMiddleware

'/hello' do
ello World'

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:

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

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.

You can find useful middleware in rack, rack-contrib, or in the Rack wiki.

Testing

Sinatra tests can be written using any Rack-based testing library or framework. Rack::Test is recommended:

ire 'my_sinatra_app'
ire 'minitest/autorun'
ire 'rack/test'

s MyAppTest < Minitest::Test
clude Rack::Test::Methods

f app
Sinatra::Application
d

f test_my_default
get '/'
assert_equal 'Hello World!', last_response.body
d

f test_with_params
get '/meet', :name => 'Frank'
assert_equal 'Hello Frank!', last_response.body
d

f test_with_user_agent
get '/', {}, 'HTTP_USER_AGENT' => 'Songbird'
assert_equal "You're using Songbird!", last_response.body
d

Note: If you are using Sinatra in the modular style, replace Sinatra::Application above with the class name of your app.

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 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:

ire 'sinatra/base'

s MyApp < Sinatra::Base
t :sessions, true
t :foo, 'bar'

t '/' do
'Hello world!'
d

The methods available to Sinatra::Base subclasses are exactly the same as those available via the top-level DSL. Most top-level apps can be converted to Sinatra::Base components with two modifications:

Sinatra::Base is a blank slate. Most options are disabled by default, including the built-in server. See Configuring Settings for details on available options and their behavior. If you want behavior more similar to when you define your app at the top level (also known as Classic style), you can subclass Sinatra::Application:

ire 'sinatra/base'

s MyApp < Sinatra::Application
t '/' do
'Hello world!'
d
Modular vs. Classic Style

Contrary to common belief, there is nothing wrong with the classic style. If it suits your application, you do not have to switch to a modular application.

The main disadvantage of using the classic style rather than the modular style is that you will only have one Sinatra application per Ruby process. If you plan to use more than one, switch to the modular style. There is no reason you cannot mix the modular and the classic styles.

If switching from one style to the other, you should be aware of slightly different default settings:

Setting Classic Modular Modular
app_file file loading sinatra file subclassing Sinatra::Base file subclassing Sinatra::Application
run $0 == app_file false false
logging true false true
method_override true false true
inline_templates true false true
static true File.exist?(public_folder) true
Serving a Modular Application

There are two common options for starting a modular app, actively starting with run!:

_app.rb
ire 'sinatra/base'

s MyApp < Sinatra::Base
... app code here ...

start the server if ruby file executed directly
n! if app_file == $0

Start with:

 my_app.rb

Or with a config.ru file, which allows using any Rack handler:

nfig.ru (run with rackup)
ire './my_app'
MyApp

Run:

up -p 4567
Using a Classic Style Application with a config.ru

Write your app file:

p.rb
ire 'sinatra'

'/' do
ello world!'

And a corresponding config.ru:

ire './app'
Sinatra::Application
When to use a config.ru?

A config.ru file is recommended if:

There is no need to switch to a config.ru simply because you switched to the modular style, and you don't have to use the 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/Hanami/Roda/…):

ire 'sinatra/base'

s LoginScreen < Sinatra::Base
able :sessions

t('/login') { haml :login }

st('/login') do
if params['name'] == 'admin' && params['password'] == 'admin'
  session['user_name'] = params['name']
else
  redirect '/login'
end
d


s MyApp < Sinatra::Base
middleware will run before filters
e LoginScreen

fore do
unless session['user_name']
  halt "Access denied, please <a href='/login'>login</a>."
end
d

t('/') { "Hello #{session['user_name']}." }
Dynamic Application Creation

Sometimes you want to create new applications at runtime without having to assign them to a constant. You can do this with Sinatra.new:

ire 'sinatra/base'
pp = Sinatra.new { get('/') { "hi" } }
pp.run!

It takes the application to inherit from as an optional argument:

nfig.ru (run with rackup)
ire 'sinatra/base'

roller = Sinatra.new do
able :logging
lpers MyHelpers


'/a') do
n Sinatra.new(controller) { get('/') { 'a' } }


'/b') do
n Sinatra.new(controller) { get('/') { 'b' } }

This is especially useful for testing Sinatra extensions or using Sinatra in your own library.

This also makes using Sinatra as middleware extremely easy:

ire 'sinatra/base'

Sinatra do
t('/') { ... }


RailsProject::Application
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 or session objects, as there is only a single application class for all requests.

Options created via set are methods at class level:

s MyApp < Sinatra::Base
Hey, I'm in the application scope!
t :foo, 42
o # => 42

t '/foo' do
# Hey, I'm no longer in the application scope!
d

You have the application scope binding inside:

You can reach the scope object (the class) like this:

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 objects or call rendering methods like erb or haml. You can access the application scope from within the request scope via the settings helper:

s MyApp < Sinatra::Base
Hey, I'm in the application scope!
t '/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!"
d

You have the request scope binding inside:

Delegation Scope

The delegation scope just forwards methods to the class scope. However, it does not behave exactly 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:

Have a look at the code for yourself: here's the Sinatra::Delegator mixin being extending the main object.

Command Line

Sinatra applications can be run directly:

 myapp.rb [-h] [-x] [-q] [-e ENVIRONMENT] [-p PORT] [-o HOST] [-s HANDLER]

Options are:

 help
 set the port (default is 4567)
 set the host (default is 0.0.0.0)
 set the environment (default is development)
 specify rack server/handler (default is thin)
 turn on quiet mode for server (default is off)
 turn on the mutex lock (default is off)
Multi-threading

Paraphrasing from this StackOverflow answer by Konstantin

Sinatra doesn't impose any concurrency model, but leaves that to the underlying Rack handler (server) like Thin, Puma or WEBrick. Sinatra itself is thread-safe, so there won't be any problem if the Rack handler uses a threaded model of concurrency. This would mean that when starting the server, you'd have to specify the correct invocation method for the specific Rack handler. The following example is a demonstration of how to start a multi-threaded Thin server:

p.rb

ire 'sinatra/base'

s App < Sinatra::Base
t '/' do
"Hello, World"
d


run!

To start the server, the command would be:

 --threaded start
Requirement

The following Ruby versions are officially supported:

Ruby 2.2
2.2 is fully supported and recommended. There are currently no plans to drop official support for it.
Rubinius
Rubinius is officially supported (Rubinius >= 2.x). It is recommended to gem install puma.
JRuby
The latest stable release of JRuby is officially supported. It is not recommended to use C extensions with JRuby. It is recommended to gem install trinidad.

Versions of Ruby prior to 2.2.2 are no longer supported as of Sinatra 2.0.

We also keep an eye on upcoming Ruby versions.

The following Ruby implementations are not officially supported but still are known to run Sinatra:

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 (future releases of MRI), but we can't guarantee anything, since it is constantly moving. Expect upcoming 2.x releases to be fully supported.

Sinatra should work on any operating system supported by the chosen Ruby implementation.

If you run MacRuby, you should gem install control_tower.

Sinatra currently doesn't run on Cardinal, SmallRuby, BlueRuby or any Ruby version prior to 2.2.

The Bleeding Edge

If you would like to use Sinatra's latest bleeding-edge 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

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:

install bundler

Then, in your project directory, create a Gemfile:

ce 'https://rubygems.org'
'sinatra', :github => 'sinatra/sinatra'

her dependencies
'haml'                    # for instance, if you use haml

Note that you will have to list all your application's dependencies in the Gemfile. Sinatra's direct dependencies (Rack and Tilt) will, however, be automatically fetched and added by Bundler.

Now you can run your app like this:

le exec ruby myapp.rb
Versioning

Sinatra follows Semantic Versioning, both SemVer and SemVerTag.

Further Reading
This work is supported by the National Institutes of Health's National Center for Advancing Translational Sciences, Grant Number U24TR002306. This work is solely the responsibility of the creators and does not necessarily represent the official views of the National Institutes of Health.