An overview of Inversion of Control: what is it and, more importantly, why should anyone care?

1. the zen of IoC
diogo.lucas@gmail.com

2. back to basics (1968)

3. coupling: bad

4. cohesion: good

5. now, things evolve…

6. encapsulation interop
SOA mocking
interfaces TDD
OOD Multi-layer
inheritance
patterns
SOLID frameworks
refactoring
FAIR
OOP polymorphism

7. so, nowadays...

8. cohesion: good

9. coupling: bad

10. a subtle case of coupling

11. coupling here
var repo = new UserRepository();
var users = repo.GetAll();

12. I can’t test this thing!
What? This test hits the database?!?
This refactoring will take ages…
constructor coupling blues
How do I link this view and controller?
But this new class implements this interface!

13. enter IoC

14. IoC is a concept
(what)

15. DI is a pattern
(how)

16. lifetime dependency
injection through
concurrency safe
construction
simplest approach

17. simpler construction
injection through
flexible injection
properties
concurrency risks

18. flexible injection
injection through concurrency risks
interfaces equivalent to props
harder setup

19. the evil twin

20. lifecycle control
smaller contracts
service locator
concurrency risks
testing is a b*

21. Castle Windsor
Unity
tools of the trade
NInject
SimpleInjector

22. consequences

23. dude, where’s my code?

24. ramping + tooling

25. smell: lots of dependencies

26. man, your code already sucks

27. risk: interfaces abound

28. grain of salt + refactoring

29. risk: locators everywhere

30. KISS

31. natural pluggable design

32. overdriven Liskov

33. easy mocking

34. great enabler for tdd

35. issue: DDD & IoC mismatch

36. no easy way out

37. interception easily doable

38. added flexibility

39. good-bye to singletons

40. let the container handle this

41. tks.

42. True insight does not issue from specialized knowledge, from
membership in coteries, from doctrines or dogmas. It comes
from the preconscious intuitions of one's whole being, from one's
own code.
Everything exists in relation to other things.
Being a spectator while one is also a participant spoils
one's performance.
zen quotes
Security and changelessness are fabricated by the
ego-dominated mind and do not exit in nature. To
accept insecurity and commit oneself to the
unknown creates a relaxing faith in the universe.
In emptiness, forms are born. When one becomes
empty of the assumptions,
inferences, and judgments he has acquired over the
years, he comes close to his
original nature and is capable of conceiving original ideas
and reacting freshly.

43. fowler on IoC:
http://martinfowler.com/articles/injection.html
http://martinfowler.com/bliki/InversionOfControl.html
interception on SI:
http://simpleinjector.codeplex.com/wikipage?title=InterceptionExtensions
IoC x anemic DM
http://programmers.stackexchange.com/questions/72768/does-inversion-of-
control-promote-anemic-domain-model
image source:
http://photopin.com

44. the tao of IoC
diogo.lucas@gmail.com