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.

piscisaureus

Locate the section for your github remote in the .git/config file. It looks like this:

[remote "origin"]
	fetch = +refs/heads/*:refs/remotes/origin/*
	url = git@github.com:joyent/node.git

Now add the line fetch = +refs/pull/*/head:refs/remotes/origin/pr/* to this section. Obviously, change the github url to match your project's URL. It ends up looking like this:

gunith

/**
  * Returns a {@link Stack} having a Tree ordered in Depth First whose root is passed as the Parameter
  *
  * @param <T> The implementation of {@link Node}
  * @param treeRoot The root of the tree
  * @return The {@link Stack} of T
  */
public static <T extends Node> Stack<T> depthFirstOrder(final T treeRoot)
{
    // Main stack, where the important stuff go

Peeja

class GroupOfThingies
  attr_accessor :thingies

  # Use like this:
  #
  #   group_of_thingies = GroupOfThingies.new
  #   group_of_thingies.each do |thing|
  #     puts "Check out this awesome thing: #{thing}!"
  #   end
  #

gist:1243758

class Credentials
  include ActiveModel::Validations
  attr_accessor :screen_name, :oauth_token, :oauth_secret
  validates_presence_of :screen_name, :oauth_token, :oauth_secret, :user

  def initialize(options={})
    @errors = ActiveModel::Errors.new(self) 
    @screen_name = options[:screen_name]
    @oauth_token = options[:oauth_token]
    @oauth_secret = options[:oauth_secret]

kirs

# encoding: utf-8

class AvatarUploader < CarrierWave::Uploader::Base

  include CarrierWave::MiniMagick

  # Choose what kind of storage to use for this uploader:
  storage :file

  # Override the directory where uploaded files will be stored.

spicycode

# 0 is too far from ` ;)
set -g base-index 1

# Automatically set window title
set-window-option -g automatic-rename on
set-option -g set-titles on

#set -g default-terminal screen-256color
set -g status-keys vi
set -g history-limit 10000

jcasimir

Friendly URLs

By default, Rails applications build URLs based on the primary key -- the id column from the database. Imagine we have a Person model and associated controller. We have a person record for Bob Martin that has id number 6. The URL for his show page would be:

/people/6

But, for aesthetic or SEO purposes, we want Bob's name in the URL. The last segment, the 6 here, is called the "slug". Let's look at a few ways to implement better slugs.

manast

function interval(duration, fn){
  var _this = this
  this.baseline = undefined
  
  this.run = function(){
    if(_this.baseline === undefined){
      _this.baseline = new Date().getTime()
    }
    fn()
    var end = new Date().getTime()

scottwater

require 'resque/server'

class SecureResqueServer < Resque::Server

  before do
    redirect '/' unless some_condition_is_met! 
  end
 
end