jnunemaker

Why You Should Never Use An ORM

Having built two object mappers in Ruby (MongoMapper and ToyStore), I would like to 
throw out a crazy thought. What if, on your next project, you ditch the ORM. 

No ActiveRecord. No DataMapper. No anything. Just you and a lower level driver, whispering
sweet nothings into Ruby classes and modules. Could you? Would you? DARE you? 

We Rubyists are all about aesthetics, right? We love declaring has_many and belongs_to!
Scope this! Boom! Instant magic happens behind the scenes. Fancy proxies are assembled, 

jnunemaker

require 'pp'
require 'zlib'
require 'benchmark'
require 'rubygems'
require 'active_support/gzip'
require 'mongo_mapper'

MongoMapper.database = 'testing'
MongoMapper.database.collections.each(&:remove)

jnunemaker

# gem install sunspot_rails
class Foo
  include MongoMapper::Document
  include Sunspot::Rails::Searchable

  key :title, String

  searchable do
    text :title
  end

jnunemaker

module PageViewsByMonth
  def map
    <<-MAP
      function() {…}
    MAP
  end
  
  def reduce
    <<-REDUCE
      function() {…}

jnunemaker

function parse_git_branch() {
  git branch 2> /dev/null | sed -e '/^[^*]/d' -e 's/* \(.*\)/(\1)/'
}

RED="\[\033[0;31m\]"
YELLOW="\[\033[0;33m\]"
GREEN="\[\033[0;32m\]"
PS1="$RED\$(date +%H:%M) \w$YELLOW \$(parse_git_branch)$GREEN\$ "

jnunemaker

require 'pp'
require 'rubygems'
require 'mongo_mapper'

MongoMapper.database = 'testing'

class Comment
  include MongoMapper::EmbeddedDocument
end

jnunemaker

# I need class C to call the foo method for each module included
# that has the method foo. Order does not matter as much as each
# method getting called. alias method chain?

module A
  def foo
    super
    puts 'a'
  end
end

jnunemaker

class Stylesheet
  include MongoMapper::Document

  class Processor
    def self.errors
      []
    end

    attr_reader :contents

jnunemaker

# Patch until MM 0.7.6 which fixes this:
# http://github.com/jnunemaker/mongomapper/commit/a721b66d9bc9ef78a5ce32dd2eb36d24abd4b953
module SetWithTypecasting
  def self.included(model)
    model.plugin SetWithTypecasting
  end

  module ClassMethods
    def set(*args)
      criteria, updates = criteria_and_keys_from_args(args)

jnunemaker

module ValidatesExistenceOfPlugin
  def self.included(model)
    model.plugin ValidatesExistenceOfPlugin
  end
  
  module ClassMethods
    def validates_existence_of(*args)
      add_validations(args, ValidatesExistenceOfPlugin::ValidatesExistenceOf)
    end
  end