A short presentation on Rack middleware I gave at the 10/21/2010 NovaRUG.

1. Rack
Scott Leberknight

3. HTTP
make request, get response

4. Request
a hash containing the environment
(headers, params, input stream)

5. Response
status, headers, body

6. Simplest Rack App..

7. class Hello status
def call(env) headers
[
200,
{ "Content-Type" => "text/plain" },
[ "Hello!", "Having fun yet?" ]
]
end
end body

8. Middleware Order Matters !

9. middlewares call() each other...
and act like chain of response filters...
...so the order you use them matters!

10. init with app
class Reverse
def initialize(app) first, Call the app
@app = app
end
def call(env)
status, headers, body = @app.call(env)
[status, headers, body.map { |b| b.reverse }]
end
end
then, do your stuff

11. use Rack::ContentLength
use RackExamples::Paragraphizer
use RackExamples::Upcase
use
use
RackExamples::Downcase
RackExamples::Reverse
Is output upper or
app = lambda { |env| [
lower case?
200,
{ 'Content-Type' => 'text/html' },
["Dammit, I'm mad!",
"Was it a rat I saw?",
"Madam, I'm Adam"]
] }
run app
11

12. use Rack::ContentLength
use RackExamples::Paragraphizer
use RackExamples::Downcase
use RackExamples::Upcase
use RackExamples::Reverse How about now?
app = lambda { |env| [
200,
{ 'Content-Type' => 'text/html' },
["Dammit, I'm mad!",
"Was it a rat I saw?",
"Madam, I'm Adam"]
] }
run app
12

13. "Off t he Shelf"

14. Rack::ShowExceptions
Rack::MailExceptions
Rack::CommonLogger
Rack::ContentLength
Rack::JSON
ActionController::StringCoercion
Rack::ETag
Rack::Deflater
...and lots more

15. Baked into Ra
ils

16. $ rake middleware
(in /Users/sleberkn/Projects/my-niclabs)
use Rack::Lock
use ActionController::Failsafe
use ActionController::Session::CookieStore, #<Proc:0x00000001017acf18@(eval):8>
use ActionController::ParamsParser
use Rack::MethodOverride
use Rack::Head
use ActionController::StringCoercion
use Rack::Deflater
use Sass::Plugin::Rack
use ActiveRecord::ConnectionAdapters::ConnectionManagement
use ActiveRecord::QueryCache
run ActionController::Dispatcher.new

17. Summary

20. References

21. http://lmgtfy.com/?q=ruby+rack
http://www.letmebingthatforyou.com/?q=ruby+rack

22. Image credits
Shelf
thedesignblog.org/entry/odersoding-storage-system-doubles-as-a-room-divider/
Cool
newgeography.com
Baking
haileythebaketress.blogspot.com
Json
nearinfinity.com

23. scott.leberknight@nearinfinity.com
www.nearinfinity.com/blogs/
twitter: sleberknight