How to get Sinatra to auto-reload the file after each change?

Question

See the Sinatra FAQ,

"How do I make my Sinatra app reload on changes?"

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

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

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

 $ gem install rerun

Now if you start your Sinatra app like this:

$ ruby app.rb

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

$ rerun 'ruby app.rb'

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

$ rerun 'rackup'

You get the idea.

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

gem install sinatra-reloader

require 'sinatra'
require 'sinatra/reloader'

Note: it will reload only sinatra handlers (and, maybe some sinatra server configuration commands), but not custom files, which you have to reload manually.

UPD after 9 years: seems like it is already possible to reload other files using also_reload, dont_reload and after_reload -- https://github.com/sinatra/sinatra/pull/1150

You can use the rerun gem.

gem install rerun
rerun 'ruby app.rb' 

OR if you are using rackup

rerun 'rackup'

gem install sinatra-reloader

require 'sinatra/base'
require "sinatra/reloader"

class MyApp < Sinatra::Base
  register Sinatra::Reloader

  get '/' do
    "Hello Testing1!"
  end
end

You may want to set environment variable to development and conditionally load the gem.

When you run the application with Passenger Standalone, just create a tmp/always_restart file:

$ touch tmp/always_restart.txt

See Passenger documentation for more info.

I like the Shotgun gem. If you're using a modular Sinatra app and have a config.ru file it's easy to run.

shotgun config.ru

Check the gem out here. It's fairly straight forward and no configuration needed.