Web "Hello World" in Ruby without RoR!

If you want to understand how things work beyond what's under the hood, the first good step is to try to write something from scratch. So, in this post, I will show you how to write a 'hello world' app for the web in pure Ruby. Above, you'll find the simple 'Hello World' code example.

class MyApp
 def say_hello
   "Hello World"
 end
end
MyApp.new.say_hello

Now we need to turn this code into a Rack app. Rack is an interface for developing web applications in Ruby. The structure of a Rack app looks like this:

run do |env|
  [200, {}, ["Hello World"]]
end

In this case, the code works like this:

class MyApp
 def say_hello
   "Hello World"
 end
end

myapp = proc do |env|
  [200, {'Content-Type' => 'text/plain'}, [MyApp.new.say_hello]]
end
run myapp

Run this using the rackup gem or another supported web server.(read more here)

rackup myapp.ru
--> Puma starting in single mode...
--> * Version 4.2.0 (ruby 2.6.5-p114), codename: Distant Airhorns
--> * Min threads: 0, max threads: 16
--> * Environment: development
--> * Listening on tcp://127.0.0.1:9292
--> * Listening on tcp://[::1]:9292
--> Use Ctrl-C to stop

You can access the app by typing in your browser. 127.0.0.1:9292.