Building Web Applications with

Kemal

@sdogruyol

paris.rb 

07.06.2016

Serdar Doğruyol

Lead Developer - Protel Turkey

@sdogruyol

• Rubyist, Crystal enthusiast
• Ruby Turkey, Crystal Turkey Organizer
• Open source developer
• Literally Polyglot

we <3 ruby

Expressive
Powerful
OOP

+

The superb performance of C 

we <3 crystal

Kemal

http://kemalcr.com

Simple
Fast
Featured

• RESTful
• Built-in WebSocket
• JSON
• Static File Serving
• Pluggable Middlewares
• View templating

require "kemal"

get "/" do
.. show something ..
end

post "/" do
.. create something ..
end

put "/" do
.. replace something ..
end

patch "/" do
.. modify something ..
end

delete "/" do
.. annihilate something ..
end

Kemal.run

REST

WebSocket

# A simple chat server
require "kemal"

messages = [] of String
sockets = [] of HTTP::WebSocket

public_folder "src/assets"

get "/" do
  render "src/views/index.ecr"
end

ws "/" do |socket|
  sockets.push socket
  socket.on_message do |message|
    messages.push message
    sockets.each do |s|
      s.send messages.to_json
    end
  end
end

http://kemal-react-chat.herokuapp.com

View Engine

<h1>This is just like ERB!</h1>

<p>Let's run some Crystal Code</p>

<% some_var = "Serdar %>

<%= Process.pid %>

ECR

h1 This is just like HAML!

p Let's run some Crystal code.

- some_var = "Serdar"
= Process.pid

Slang

Fast

get "/" do 
  "Hello world!"
end

HTTP

Websocket

https://gist.github.com/sdogruyol/bdd400a6eac13e26228e

Who uses Kemal

Crystal for Rubyists

http://www.crystalforrubyists.com

Questions?

Thanks!

@sdogruyol

https://slides.com/sdogruyol/building-web-apps-with-kemal-parisrb