This document discusses various design patterns used in Symfony2 frameworks such as Front Controller, Decorator, Factory Method, Abstract Factory, Builder, Proxy, Mediator, Strategy, Data Mapper, Visitor, and MVC. It also discusses anti-patterns like Design for the Sake of Design, Overengineering, The Blob, Reinventing the Wheel, and Spaghetti Code. The key principles discussed are inversion of control, dependency injection, and decoupling. References for further reading on design patterns, inversion of control, and anti-patterns are also provided.

1. DESIGN PATTERNS INSIDE SYMFONY2
Nanos gigantium
humeris insidentes

2. GIANTS

3. liurrrgio
GIORGIO CEFARO
@giorrrgio
GIULIO DE DONATO
@liuggio

4. DESIGN PATTERN?

5. A solution of a
problem in a context
James O. Coplien (1994)
DESIGN PATTERN

6. “ For me a pattern is
primarily a way to chunk up
advice about a topic “
DESIGN PATTERN

7. #1

8. INTENT:
A controller that handles
all requests for a Web site
FRONT CONTROLLER

9. FRONT CONTROLLER
web/app.php

10. FRONT CONTROLLER ... and ?
web/app.php

11. INTENT:
Attach additional responsibilities
to an object dynamically.
Decorators provide a flexible
alternative to subclassing for
extending functionality.
DECORATOR

12. DECORATOR
SymfonyComponentHttpKernelHttpCacheHttpCache

13. U DUNNO
HttpKernelInterface?
SymfonyComponentHttpKernelHttpKernelInterface

14. KERNEL AND SERVICE CONTAINER
SymfonyComponentHttpKernelKernel

16. INVERSION OF CONTROL
INTENT:
Inversion of control is a style
of software construction where
reusable code controls the execution
of problem-specific code

17. 1988
INVERSION OF CONTROL

18. “ Inversion of control is a common
characteristic of frameworks,
so saying that these lightweight containers
are special because they use inversion of
control is like saying my car is special
because it has wheels.”

19. “ DON’T CALL US
WE’LL CALL YOU ”
INVERSION OF CONTROL
HOLLYWOOD PRINCIPLE:

20. INVERSION OF CONTROL

21. "Dependency Injection is where
components are given their
dependencies through their
constructors, methods, or directly
into fields."
PICO CONTAINER DEFINITION:

22. Dependency injection allows the
removal of hard-coded dependencies
and makes it possible to change
them, whether at run-time or compile-
time.

23. INJECTING A TRANSPORT INSIDE A MAILER

24. - FIGHT OF THE DAY -
SERVICE CONTAINER
vs
DEPENDENCY INJECTION

25. INVERSION OF CONTROL
INTENT:
DECOUPLE
DECOUPLE
DECOUPLE
DECOUPLE
DECOUPLE
DECOUPLE
DECOUPLE DECOUPL
DECOUPLE
DECOUPLE

26. ??
DEPENDENCY INJECTION AND FRAMEWORKS
Grafico con spaghetti, infermiera che fa la
puntura, lista della spesa per l'antipattern
service locator, qualcosa di galattico per
l'enhanced injection (tipo pulp fiction)
DI
DIC
http://www.loosecouplings.com/2011/01/dependency-injection-using-di-container.html

27. INTENT:
Define an interface for creating an object,
but let subclasses decide which class
to instantiate.
Factory Method lets a class defer instantiation to
subclasses.
FACTORY METHOD

28. FACTORY METHOD - DO IT WITH THE DIC

29. INTENT:
Provide an interface for creating
families of related or dependent
objects without
specifying their concrete classes.
ABSTRACT FACTORY

30. ABSTRACT FACTORY - SecurityFactoryInterface
SymfonyBundleSecurityBundleDependencyInjectionSecurityFactorySecurityFactoryInterface

31. INTENT:
Separate the construction of a
complex object from its
representation so that the same
construction process can create
different representations.
BUILDER

32. FORM BUILDER
SymfonyComponentFormFormBuilderInterface

33. FORM BUILDER

34. INTENT:
Provide a surrogate or
placeholder for another
object to control access to it.
PROXY

35. DOCTRINE PROXY
app/cache/doctrine/odm/Proxies/ ...

36. INTENT:
Define an object that encapsulates how a set
of objects interact. Mediator promotes loose
coupling by keeping objects from referring to
each other explicitly, and it lets you vary their
interaction independently.
MEDIATOR

37. MEDIATOR
RouterListener
Kernel :: REQUEST EVENT DISPATCHERSessionListener
Firewall
LocaleListener
ProfilerListener
FragmentListener

38. INTENT:
Defines a family of algorithms, encapsulate
each one, and make them interchangeable.
Strategy lets the algorithm vary independently
from clients that use it.
STRATEGY aka POLICY

39. FragmentRendererInterface
SymfonyComponentHttpKernelFragmentFragmentRendererInterface

40. Fragment Renderers
SymfonyComponentHttpKernelFragment...

41. INTENT:
A layer of Mappers that moves data between
objects and a database while keeping them
independent of each other and the mapper
itself.
DATA MAPPER

42. INTENT:
Represent an operation to be performed on
the elements of an object structure.
Visitor lets you define a new operation without
changing the classes of the elements on which
it operates.
VISITOR

43. VALIDATION VISITOR
SymfonyComponentValidator..

44. MVC
Controller
View
Model

45. ANTI-PATTERNANTI-PATTERNANTI-PATTERN
AbstractionInversion, AccidentalComplexity, AccidentalInclusion, AddingEpicycles, AlcoholFueledDevelopment,
AmbiguousViewpoint, AnalogyBreakdownAntiPattern, AnalysisParalysis, AnAthena, AppointedTeam, ArchitectsDontCode,
ArchitectsPlayGolf, ArchitectureAsRequirements, ArchitectureByImplication, AsynchronousUnitTesting,
AutogeneratedStovepipeAntiPattern, BandAid, BearTrap?, BigBallOfMud, BlameStorming, BlowhardJamboree, BoatAnchor,
CargoCult, CarParkSyndrome, CascadingDialogBoxesAntiPattern, ContinuousObsolescence, ConfusionOfObjectives, ControlFreak,
CopyAndPasteProgramming, CornCob, CoverYourAssets, CreepingFeaturitis, CrciCards, CryptoCracy, DeadEnd, DeathByPlanning,
DecisionByArithmetic, DesignByCommittee, DesignForTheSakeOfDesign., DiscordantRewardMechanisms, DoerAndKnower,
DryWaterhole, EgalitarianCompensation, EmailIsDangerous, EmperorsNewClothes, EmpireBuilding, ExceptionFunnel,
FalseEconomy, FalseSurrogateEndpoint, FearOfSuccess, FireDrill, FloatingPointCurrency, FloatingPointFractions, FoolTrap,
FunctionalDecomposition, FungibleTeams, FungibleProjectManager, GeographicallyDistributedDevelopment,
GiveMeEstimatesNow, GlassWall, GodClass, GoldenHammer, GroundHogDayProject, HalfDoneIsEnough, HeirApparent,
HeroCulture, HiddenRequirements, IdiotProofProcess., IfItIsWorkingDontChange, IfOk, InappropriateTechnicalObjective,
InputKludge, ItsAnOperatorProblem, JobKeeper, JumbleAntipattern, JunkyardCoding, KillTwoBirdsWithOneStone,
KitchenSinkDesign, LavaFlow, LeadingRequest, MagicContainer, ManagerControlsProcess, MushroomManagement, Nationalism,
NetNegativeProducingProgrammer, NotInventedHere, NotTheAppropriateProtocol, NullFlag, OverGeneralizationOfBusinessLogic,
OverUseOfPatterns, PathOfLeastResistance, ParsingHtmlWithRegex, PassingNullsToConstructors,
PlugCompatibleInterchangeableEngineers, PoliticsOrientedArchitecture, PolterGeists, ReinventingTheWheel, ReinventTheWheel,
RollYourOwnDatabase, RequirementsTossedOverTheWall, RubeGoldbergMachine, ScapeGoat, SeagullManagement, SecretSociety,
SellingaProductYouCantRealize, ShootTheMessenger, SingleFunctionExitPoint, SmokeAndMirrors, SoftwareMerger,
SpaghettiCode, SpecifyNothing, StandingOnTheShouldersOfMidgets, StovepipeAntiPattern, StringWithoutLength, SumoMarriage,
SweepItUnderTheRugAntiPattern, SwissArmyKnife, ThatsNotReallyAnIssue, TheBlob, TheCustomersAreIdiots,
TheGrandOldDukeOfYork, TheProcessIsTheDeliverable, TheyUnderstoodMe, ThrownOverTheWall, TowerOfVoodoo, TrainTheTrainer,
UntestedButFinished, VendorLockIn, ViewgraphEngineering, VietnamWarAntiPattern, VoodooChickenCoding,
WalkingThroughaMineField, WarmBodies, WeAreIdiots, WolfTicket, YetAnotherMeetingWillSolveIt, YetAnotherThreadWillSolveIt,

46. ANTI PATTERNS
DESIGN
FOR THE SAKE OF DESIGN
“I only ship the perfection"

47. ANTI PATTERNS
OVER ENGINEERING
OVERUSE OF PATTERNS

48. ANTI PATTERNS
THE BLOB
BIG BALL OF MUD

49. ANTI PATTERNS
GLOBALIZING
STANDING ON THE SHOULDER OF THE MIDGETS

50. ANTI PATTERNS
REINVENTING THE WHEEL
NIH SYNDROME

51. SPAGHETTI CODE
SPAGHETTI WITH MEATBALL
LASAGNA CODE
RAVIOLI CODE
RAVIOLI CODE

52. code spends
more time being read
and maintained than
being created

53. DECOUPLE

54. DECOUPLE

55. DECOUPLE.

56. GOOD QUESTIONS
ARE BETTER THAN
GOOD ANSWERS

57. 1. https://gist.github.com/giorrrgio/d4395afe470a1ad223e0
2. http://12factor.net
3. http://obvioushints.blogspot.it/2008/12/symfony-design-patterns.html
4. http://c2.com/cgi/wiki?AntiPatternsCatalog
5. http://martinfowler.com/bliki/InversionOfControl.html
6. http://martinfowler.com/articles/injection.html
REFERENCES