Sinatra Cheat Sheet

Core Concepts & Setup

Install Sinatra via RubyGems:

gem install sinatra

For logging:

gem install sinatra-contrib

A simple Sinatra application structure:

require 'sinatra'

get '/' do
  'Hello, world!'
end

Running the app:

ruby your_app.rb

`set :port, 8080`	Sets the port the application listens on.
`set :environment, :production`	Sets the environment (development, production, test).
`enable :sessions`	Enables session support.

Accessing parameters from the route:

get '/hello/:name' do
  # Matches /hello/foo and /hello/bar
  # params[:name] will be 'foo' or 'bar'
  "Hello #{params[:name]}!"
end

Optional parameters:

get '/posts/:id?' do
  # Matches /posts/123 and /posts
  # params[:id] will be '123' or nil
end

Splats (capturing multiple segments):

get '/download/*/*' do
  # Matches /download/path/to/file.txt
  # params[:splat] will be ['path/to', 'file.txt']
end

Rendering a view:

get '/' do
  erb :index
end

This will render views/index.erb.

Specifying a different template path:

get '/' do
  erb :index, :views => settings.template_path
end

`erb`	Embedded Ruby templates.
`haml`	Haml templates (requires `haml` gem).
`slim`	Slim templates (requires `slim` gem).
`liquid`	Liquid templates (requires `liquid` gem).
`markdown`	Markdown templates (requires `rdiscount` or similar gem).

Using a layout:

get '/' do
  erb :index, :layout => :default
end

This will render views/index.erb inside views/default.erb.

Disabling layout:

get '/' do
  erb :index, :layout => false
end

Defining a helper:

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

get '/' do
  bar('World')
end

`halt`	Immediately stops request processing.
`pass`	Passes control to the next matching route.
`redirect 'url'`	Redirects the client to the given URL.
`session`	Access the session hash (if sessions are enabled).
`params`	Access request parameters.

Using extensions:

require 'sinatra/reloader'

configure :development do
  register Sinatra::Reloader
end

Common extensions:

Details

Frameworks & Libraries / Sinatra

March 03, 2025 00:54

routing

ruby

sinatra

web development

web framework