Lecture demistifying monads. After talking a bit about Monoids and Functor I explain a functional design technics which is Monad through the refactoring of a JDBC code. Talk given at The Developper Conference in Porto Alegre in 2014 (http://www.thedevelopersconference.com.br), Code source of the presentation is in my github: https://github.com/toff63/monads-in-practice-tdc

1. Monads in Practice
Christophe Marchal | Software Architect

2. A couple of links
christophe.marchal@ilegra.com
@toff63
http://github.com/toff63
http://francesbagual.net

3. Disclaimer

4. Manage complexity with Monad

5. Study Monads online is hard

6. Academic talks
Functor
Monoids
Monads
Category
theory

7. Category Theory

8. Function
Monoids
Associative
( 1 + 2 ) + 3 = 1 + ( 2 + 3 )
InitiAl Value
Result stay in the same
category

9. Monoid Example

10. Monoid

11. Functor
Things that can be map over
capacity BEHaviour
map

12. Functor: Example

13. Functor: Example

14. Monads

15. Problem it solves

16. Scenario
F 1 F 2

17. sweet
Monads Rules: function to create it

18. Broken Composition
F 1
F 2 sweet

19. Monads Rules: You need a Functor
F 1
map ( f 2 )
sweet

20. Scenario
F 1 F 3
sweet

21. Problem: Nested Monad
F 1
sweet
map ( f 3 )
sweet

22. F 1
sweet
Flatmap ( f 3 )
Monads Rules: You need a Flatmap

24. Business rule
TRUE False
age > 18
Authorized Not
Authorized

25. Business rule implementation

26. What we want

27. Monad (?) Code

28. Trade-off
More code than before
Better API
Easy to reuse
Potential complexity Managed

29. Traditional Code

30. Side Effect
Our method can return either a sequence
either null

31. Exist
?
TRUE False
null ?
Riendutout quelquechose

32. Encapsulating if null with Option

33. Creating our OptionBagual

34. Code with Options

35. Business code

36. Side Effect
Our method can return either an option
[sequence] either throw an exception

37. Try!
Success Failure
Try to
execute
Gremio Inter

38. Encapsulating try/catch with Try

39. Encapsulating try/catch with Try

40. Code with Try

41. Business code

42. Connection Handling

43. No silver bullet

44. Loan Pattern

45. Final Code

46. Conclusion
● NO IFs
● Border cases handled on demand
● More declarative types
● Highlight business code
● Easy to create
● More reusable code

47. Thank You!
Christophe Marchal | Software Architect