Fitzsimmons

Building Rich Domain Models in Rails

Part 1. Decoupling Persistence

Abstract

Domain model is an effective tool for software development. It can be used to express really complex business logic, and to verify and validate the understanding of the domain among stakeholders. Building rich domain models in Rails is hard. Primarily, because of Active Record, which doesn't play well with the domain model approach.

One way to deal with this problem is to use an ORM implementing the data mapper pattern. Unfortunately, there is no production ready ORM doing that for Ruby. DataMapper 2 is going to be the first one.

Another way is to use Active Record just as a persistence mechanism and build a rich domain model on top of it. That's what I'm going to talk about here.

Fitzsimmons

var that = this;
this.player.on("audio-ended", function() {
  that.next();
});

//-------VERSUS-----------

this.player.on("audio-ended", function() {
  this.next();
}, this);

Fitzsimmons

class T
  def initialize(&block)
    self.class.send(:define_method, :runner, &block)
  end

  def do_stuff
    self.runner do |thing|
      puts thing
    end
  end

Fitzsimmons

This guide will get you started using Spark on Heroku/Cedar. Spark is basically a clone of Sinatra for Java. 'Nuff said.

Create your app

Create a single Java main class in src/main/java/HelloWorld.java:

import static spark.Spark.*;
import spark.*;

Fitzsimmons

tm22-s00334 rabbitmq # ls -l
total 59624
-rw-r--r-- 1 rabbitmq rabbitmq        0 Mar 27 03:10 [email protected]
-rw-r--r-- 1 rabbitmq rabbitmq    94393 Mar 27 03:10 [email protected]
-rw-r--r-- 1 rabbitmq rabbitmq        0 Mar 26 03:10 [email protected]
-rw-r--r-- 1 rabbitmq rabbitmq    51897 Mar 26 03:10 [email protected]
-rw-r--r-- 1 rabbitmq rabbitmq       20 Mar 27 03:10 [email protected]
-rw-r--r-- 1 rabbitmq rabbitmq 34326652 Mar 27 11:00 [email protected]
-rw-r--r-- 1 rabbitmq rabbitmq 32088122 Mar 27 03:10 [email protected]
-rw-r--r-- 1 rabbitmq rabbitmq        0 Mar 26 03:10 [email protected]

Fitzsimmons

require 'benchmark'

require 'rubygems'
require 'bunny'

m = "<event>
  <string1>123456790123456790123456790123456790</string1>
  <string2>123456790123456790123456790123456790</string2>
  <string2>123456790123456790123456790123456790</string2>
  <string2>123456790123456790123456790123456790</string2>

Fitzsimmons

nulogy@tm22-s00081 ~ $ sudo /usr/sbin/passenger-status
----------- General information -----------
max      = 4
count    = 4
active   = 4
inactive = 0
Waiting on global queue: 2

----------- Application groups -----------
/data/nulogy/current:

Fitzsimmons

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                                                 
16965 nulogy    18   0 2372m 1.5g  100 D   17 41.8 267:41.66 Rack: /data/nulogy/current                                              
 1466 nulogy    18   0  667m 527m  392 R    9 14.0   3:45.65 Rack: /data/nulogy/current                                              
 1457 nulogy    18   0  659m 523m  420 R   18 13.9   3:32.19 Rack: /data/nulogy/current                                              
 1460 nulogy    18   0  585m 451m  680 R   18 12.0   3:14.81 Rack: /data/nulogy/current                                              
 1407 nulogy    24   0  522m 344m  336 S    0  9.1   0:33.26 Passenger ApplicationSpawner: /data/nulogy/current                      
 1463 nulogy    18   0  554m 316m  336 D   13  8.4   1:56.39 Rack: /data/nulogy/current                                              
11549 nulogy    18   0  789m 178m   84 R   14  4.7  55:40.76 Rack: /data/nulogy/curren

Fitzsimmons

# Customize to your needs...
be() {
  if [[ -a Gemfile ]]; then
    bundle exec $*
  else
    command $*
  fi
}

Fitzsimmons

### ZSH
### Add one of these to your .zshrc

# Outputs a github link that you can click on to see the diff
devreview() {
  if [[ -n $1 ]]; then
    git log --pretty=oneline | egrep "Merge branch '${1}.*' into (dev|release|rails_3)" | awk '{print "https://github.com/nulogy/packmanager/commit/" $1}'
  fi
}