Ruby Entity Manager, experimental ORM based on SOLID principles and Domain Driven Design

1. ActiveDomain
An Experimental SOLID ORM
Thursday, December 2, 2010

2. Me!
• Franck Verrot
• http://twitter.com/cesariogw
• http://github.com/cesario
• Currently awesoming at Leadformance
Thursday, December 2, 2010

3. This is all about
• Software architecture
• Principles I believe in
• Current implementations and their limits
• ActiveDomain!
Thursday, December 2, 2010

4. Software Architecture
Thursday, December 2, 2010

5. SOLID
principles
• Single Responsibility
• Open/Close
• Liskov Substitution
• Interface Segregation
• Dependency Inversion
Thursday, December 2, 2010

6. Inspired by DDD
• The cover sucks
• DDD > Your Mom
• Entities,Value Objects
• Context Boundaries, ...
Thursday, December 2, 2010

7. Current
implementations
Thursday, December 2, 2010

8. You do that
ActiveRecord
1 class Post 1 class Post < ActiveRecord::Base
2 include DataMapper::Resource 2 has_many :comments
3 3 end
4 property :id, Serial
5
6 has n, :comments
7 end
Thursday, December 2, 2010

9. Pros Cons
• Convention • Fine-tuning
• High Level of Abstraction • Magic can be misleading
• Easy to learn • Hard to specialize
Thursday, December 2, 2010

10. You might do that too
ActiveRecord
1 class Post 1 class Post < ActiveRecord::Base
2 include DataMapper::Resource 2 vestal_version
3 is :nested_set, 3 acts_as_paranoid
:scope => [ :user_id ] 4 set_table_name ‘articles’
4 property :id, Serial 5 set_primary_key ‘arti_id’
5 property :title, String 6 has_many :comments,
6 has n, :comments 7 :through => :articles,
7 end 8 :foreign_key => :id
9 before_validate :do_stuff
10 def do_stuff
11 ...
12 end
13 end
Thursday, December 2, 2010

11. Architecture at risk
(scary title I know)
Thursday, December 2, 2010

12. Issues
• Separation of concerns
• Testing the layers independently
• Efficiency ( Transactions, Memory footprint)
• Side effects (Lazy loading, non-“PORO”)
Thursday, December 2, 2010

13. ActiveDomain
Thursday, December 2, 2010

14. Features
• “Plain Old Ruby Object”
• Unit of Work
• DB agnostic from the start
• Could be used to build an AR-like ORM
• Identity Mapping
Thursday, December 2, 2010

15. In Action 1/4
describe "User" do
it "has many posts" do
user = Entity::User.new :email => 'test@test.com'
user.posts << Entity::Post.new(:title => 'Test post')
user.should have(1).post
end
end
module Entity
class User
include ActiveModel::Validations
attr_reader :id
attr_accessor :email, :name, :posts
validates :email, :presence => true
def who
"i am #{name} (#{email})"
end
def initialize args = {}
self.email = args.fetch(:email, nil)
self.name = args.fetch(:name, nil)
self.posts = args.fetch(:posts, [])
end
end
end
Thursday, December 2, 2010

16. In Action 2/4
module Repository
class User < ActiveDomain::Repository::Base
adapter :mysql
table :users
dsn 'mysql://root:@localhost:3306/test'
end
end
Thursday, December 2, 2010

17. In Action 3/4
module Mapping
class User < ActiveDomain::Mapper::Base
entity Entity::User
repository Repository::User
map {
id :id
email :email
}
associations {
has_many Entity::Post,
:as => :posts,
:conditions => { :id => :author_id }
}
end
end
Thursday, December 2, 2010

18. In Action 4/4
$EM = ActiveDomain::EntityManager::Base.new do
register :users, Mapping::User
end
user = Entity::User.new :email => 'test@test.com'
$EM.users.attach(user) #object marked as new
$EM.flush #object persisted
user_found = $EM.users.find(:email => "test@test.com")
user == user_found # => true
Thursday, December 2, 2010

19. Is it ready yet?
• No!
• Associations don’t work yet
• Identity mapper in progress
• Will be released when it’ll work :)
Thursday, December 2, 2010

20. Thanks for listening!
Q&A
Thursday, December 2, 2010