Presented at the Functional Swift Conference 2015.

1. You Used To Inject Me
In Your Constructor
- Functional Programming In Swift

2. Hello, I’m
Veronica Ray!

3. –Dependency Injection Demystified
“Dependency injection
means giving an object its
instance variables.
Really.
That's it.”

4. WHY

6. WHY
•Clear declaration of
dependencies
•Composition
•Easy customization

7. WHY
•Clear
ownership
•Testability

8. FRAMEWORK

10. LAYER OF
ABSTRACTION

11. SUPER
LINEAR

12. SMART
FRAMEWORKS

13. LAZY
EVALUATION

14. –HaskellWiki
“…expressions are not
evaluated when they are
bound to variables, but their
evaluation is deferred until
their results are needed by
other computations. ”

15. –HaskellWiki
“…Pure computations ..can
be performed at any time
and still yield the same
result.

16. –HaskellWiki
“This makes it possible to
defer the computation of
values until they are
needed, that is, to compute
them lazily. ”

17. Lazy evaluation
Brought to you
by functional
programming

18. MEMOIZATION

19. –Python 3 Tutorial
“ If the same input or a
function call with the same
parameters is used, the
previously stored results can
be used again and
unnecessary calculation are
avoided.”

20. SCOPES

21. TYPHOON

22. TyphoonScopeSingleton
TyphoonScopeLazySingleton

23. SWINJECT

24. ObjectScope.Container

27. ISSUES

28. WE NEED A
RESOLUTION

29. DI IN SWIFT
•constructor
injection
•reader monad

30. DI IN SWIFT
•constructor
injection
•reader monad

31. BearWithMe
Find fiends to
hibernate with
during the winter

36. –In today’s post-OO world, is dependency injection still relevant?
“Currently we use the same
mechanism – parameters –
to define the environment
(e.g. via constructor
parameters), as we use to
pass data around
functions.”

37. DI IN SWIFT
•constructor
injection
•reader monad

38. –Don’t Fear The Reader
“…if you break down
common dependency
injection libraries they are
just different
implementations of the
Reader Monad pattern.”

41. SIMPLE
EXAMPLE

42. DO NOTATION

43. DESUGARED

44. SWIFT

45. BearWithMe
Find fiends to
hibernate with
during the winter

48. IS THIS A GOOD
IDEA?

49. USE DEPENDENCY
INJECTION

50. LEARN MORE

51. •Swiftz
•Swift Injection
•Nick Santos
•objc.io
•adit.io

52. THANK YOU