All I Need to Know I Learned by Writing My Own Web Framework

All I Really Need to Know*
I Learned by Writing My
Own Web Framework
Ben Scofield 7 November 2008
Rubyconf

* about Ruby and the web

DSLs
DSL

Intimidate
and
Frighten
ﬂickr: cwsteeds

Rails

your custom
framework

main() {
printf(quot;hello, worldnquot;);
}

-module(hello).

-export([hello/0]).

hello() ->
io:format(quot;Hello World!~nquot;, []).

PROGRAM HELLO
PRINT*, 'Hello World!'
END

main = putStrLn quot;Hello Worldquot;

Imports System.Console

Class HelloWorld

Public Shared Sub Main()
WriteLine(quot;Hello, world!quot;)
End Sub

End Class

!greeting.
+!greeting : true <- .print(quot;Hello Worldquot;).

PHP Framework (based on Rails)

but really:

NOT FOR PRODUCTION!

ActionMailer
ActionPack
ActiveRecord
Ruby on Rails
ActiveResource
ActiveSupport
Railties

Sequel
ActiveRecord
persistence layer
DataMapper
Og

ERB
Liquid
Amrita2
templating layer
Erubis
Markaby
HAML

Ramaze
Waves
ActionPack
the middle layer
Merb Core
Sinatra
Camping

ActionMailer
Merb Helpers
utilities
ActiveSupport
Railties

Mack
CGI
Coset
SCGI
Camping
LSWS
Halcyon
Mongrel
Maveric
WEBrick
Sinatra
FastCGI
Vintage
Fuzed
Ramaze
Thin
Waves
Ebb
Merb

Rack::Lint
Rack::URLMap
Rack::Deflater
Rack::CommonLogger
middlewares
Rack::ShowExceptions
Rack::Reloader
Rack::Static
Rack::Cache

Rack::Request
utility
Rack::Response

fully-formed web applications
built on resources

Dionysus
ask me after if you don’t get the joke

Extraction ﬂickr: 95579828@N00

class Habit < Athena::Resource
def get
@habit = Habit.find(@id)
end

# ...
end

RouteMap = {
:get => {
//habit/new/ => {:resource => :habit, :template => :new},
//habit/(d+)/ => {:resource => :habit},
//habit/(d+)/edit/ => {:resource => :habit, :template => :edit}
},
:put => {
//habit/(d+)/ => {:resource => :habit}
},
:delete => {
//habit/(d+)/ => {:resource => :habit}
},
:post => {
//habit// => {:resource => :habit}
}
}

puts quot;Starting Athena applicationquot;

require 'active_record'
require File.expand_path(File.join('./vendor/athena/lib/athena'))
puts quot;... Framework loadedquot;

Athena.require_all_libs_relative_to('resources')
puts quot;... Resources loadedquot;

use Rack::Static, :urls => ['/images', '/stylesheets'], :root => 'public'
run Athena::Application.new
puts quot;... Application startednnquot;

puts quot;^C to stop the applicationquot;

module Athena
class Application
def self.root
File.join(File.dirname(__FILE__), '..', '..', '..', '..')
end

def self.route_map
@route_map ||= {
:get => {},
:post => {},
:put => {},
:delete => {}
}
@route_map
end

def call(environment)
request = Rack::Request.new(environment)
request_method = request.params['_method'] ? # ...

matching_route = Athena::Application.route_map # ...

if matching_route
resource = matching_route.last[:class].new(request, request_method)
resource.template = matching_route.last[:template]
return resource.output
else
raise Athena::BadRequest
end
end
end
end

module Athena
class Resource
extend Athena::Persistence
attr_accessor :template

def self.inherited(f)
unless f == Athena::SingletonResource
url_name = f.name.downcase
routing = url_name + id_pattern
url_pattern = /^/#{routing}$/

Athena::Application.route_map[:get][/^/#{routing}/edit$/] = # ...
Athena::Application.route_map[:post][/^/#{url_name}$/] = # ...
# ...
end
end

def self.default_resource
Athena::Application.route_map[:get][/^/$/] = {:class => # ...
end

def self.id_pattern
'/(d+)'
end

def get; raise Athena::MethodNotAllowed; end
def put; raise Athena::MethodNotAllowed; end
def post; raise Athena::MethodNotAllowed; end
def delete; raise Athena::MethodNotAllowed; end

# ...
end
end

class Habit < Athena::Resource
persist(ActiveRecord::Base) do
validates_presence_of :name
end

def get
@habit = Habit.find_by_id(@id) || Habit.new_record
end

def post
@habit = Habit.new_record(@params['habit'])
@habit.save!
end

def put
@habit = Habit.find(@id)
@habit.update_attributes!(@params['habit'])
end

def delete
Habit.find(@id).destroy
end
end

class Habits < Athena::SingletonResource
default_resource

def get
@habits = Habit.all
end

def post
@results = @params['habits'].map do |hash|
Habit.new_record(hash).save
end
end

def put
@results = @params['habits'].map do |id, hash|
Habit.find(id).update_attributes(hash)
end
end

def delete
Habit.find(:all,
:conditions => ['id IN (?)', @params['habit_ids']]
).map(&:destroy)
end
end

module Athena
module Persistence
def self.included(base)
base.class_eval do
@@persistence_class = nil
end
end

def persist(klass, &block)
pklass = Class.new(klass)

pklass.class_eval(&block)
pklass.class_eval quot;set_table_name '#{self.name}'.tableizequot;
eval quot;Persistent#{self.name} = pklassquot;

@@persistence_class = pklass
@@persistence_class.establish_connection(
YAML::load(IO.read(File.join(Athena::Application.root, # ...
)
end

def new_record(*args)
self.persistence_class.new(*args)
end

def persistence_class
@@persistence_class
end

# ...

HTTP status codes http://thoughtpad.net/alan-dean/http-headers-status.gif

rack::cache
http://tomayko.com/src/rack-cache/

module Athena
class Application
# ...

def process_params(params)
nested_pattern = /^(.+?)[(.*])/
processed = {}
params.each do |k, v|
if k =~ nested_pattern
scanned = k.scan(nested_pattern).flatten
first = scanned.first
last = scanned.last.sub(/]/, '')
if last == ''
processed[first] ||= []
processed[first] << v
else
processed[first] ||= {}
processed[first][last] = v
processed[first] = process_params(processed[first])
end
else
processed[k] = v
end
end
processed.delete('_method')
processed
end

# ...
end

Form Parameters
end

module Athena
module Persistence
def self.included(base)
base.class_eval do
@@persistence_class = nil
end
end

def persist(klass, &block)
pklass = Class.new(klass)

pklass.class_eval(&block)
pklass.class_eval quot;set_table_name '#{self.name}'.tableizequot;
eval quot;Persistent#{self.name} = pklassquot;

@@persistence_class = pklass
@@persistence_class.establish_connection(
YAML::load(IO.read(File.join(Athena::Application.root, # ...
)
end

def new_record(*args)
self.persistence_class.new(*args)
end

def persistence_class
@@persistence_class
end

# ...

Dynamic class creation

Tangled classes ﬂickr: randomurl

module Athena
module Persistence
# ...

def method_missing(name, *args)
return self.persistence_class.send(name, *args)
rescue ActiveRecord::ActiveRecordError => e
raise e
rescue
super
end
end
end

Exception Propagation

More to learn ﬂickr: glynnis

... always ﬂickr: mointrigue

http://github.com/bscofield/athena
(under construction)

Thank you!
Questions?

Ben Scofield
Development Director, Viget Labs

http://www.viget.com/extend | http://www.culann.com
ben.scofield@viget.com | bscofield@gmail.com

All I Need to Know I Learned by Writing My Own Web Framework

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