marat kamenschykov. gof patterns + rails =?

Rails + GoF Patterns

= ?Marat KamenschikovSvitla Systems Inc.

GoF = Gang of Four:

Erich GammaRichard Helm

Ralph JohnsonJohn Vlissides

Design Patterns: Elements of Reusable Object-Oriented

Software

With foreword of Grady BoochPrinted on October 21, 1994

as of July 2010, the book was in its 38th printing

500,000 copies have been sold in English and in 13 other languages.

23 reusable design patterns

3 parts:

• Structural patterns

• Creational patterns

• Behavioral patterns

Creational patterns

• Create objects for you, rather than having you instantiate objects directly

• 5 patterns: – Abstract Factory– Builder (Строитель)– Factory Method– Prototype – Singleton (Одиночка)

Structural patterns

• Class and object composition• 7 patterns:

– Adapter (Адаптер)– Bridge – Composite– Decorator– Façade (Фасад)– Flyweight (Приспособленец)– Proxy (Заместитель)

Behavioral patterns

• Communication between objects• 11 patterns:

– Chain of responsibility– Command– Interpreter– Iterator– Mediator– Memento– Observer– State– Strategy– Template method– Visitor

Project overview

• Web-interface for IP-telephony service subscribers

• 3 WSDL services

• 3+ XML services

• 5 foreign MySQL DBs

• Local MySQL DB for structuring the incoming info

DB

XML

WSDL

WSDL

WSDL

XMLXML

DB

DB

DB

DB

Web-appwith DB

Purpose of my talk:

• Which GoF patterns we were able to use?

• How did they couple with Rails?

• Results: what is good and what is bad

Project challenges

• Not GUI-oriented Servers Object structure

• Requirement to store settings in local DB on login to support several parallel sessions

• Rails

Not GUI-oriented Servers Object structure

• Web-app: single system with a straight structure – 1 root object and others are associated

• Services and remote DBs: distributed system with various authenticating procedures and ways to retrieve data

Ideal data structure (initial web-app design)

Blacklists

CallForwarding

Privacy

Message

Folder

Address

BusinessModel

Tier CreditCard

Bundle

Subscription

Feature

Number

Account

Inbox

GoogleVoice

System

Device

Services structure

Service

XML1_2

Address

XML1_3

CreditCard

XML1_1

User

customer_pk

Number

Device

pin

Login

xml_session WSDLLogin

wsdl_session

VMForwarding

VMMessages

ForeignDBs

It’s almost completely different!!!

And not only in data structure!!!

Façade

Façade

Façade

Singleton

Builder

Flyweight

Flyweight

Proxy

Façade

class ConnectionAdapter

end

Singleton

@@

Flyweight

Id | name 1 | Nick

User < ARid: 1name: Nick

User.find(1)User.find_by_id(1)

User.find_by_name(‘Nick’)

Identity map:

https://github.com/pjdavis/identity-map

Builder

• Tried to build ideal structure of what we had: FAIL!

Finally

CallForwarding

Blacklists

VoicemailNotification

Privacy

Number

Message

Folder

Action1

Subscription

Bundle

Tier

Action2

BusinessModel

UserSession

CreditCard

Action3

Address

GoogleVoiceDevice

Proxy

UserSession < AR::Base

Results

• UserSession is the only singleton and eventually Façade in Rails

• Don’t build ideal data model, build what is needed

• Identity Map requires different approach to associations but still awesome

• Lazy loading is cool!

Thank you!