A gentle introduction on the use of implicit values & conversions in Scala. It also introduces some design patterns for which implicit(s) are the building blocks. http://blog.stratio.com/developers-guide-scala-implicit-values-part/

1. Scala’s Implicits
Pablo Francisco Pérez Hidalgo (@pfcoperez)
github.com/pfcoperez

2. Scala’s Implicits
Implicit Values
Pablo Francisco Pérez Hidalgo (@pfcoperez)
github.com/pfcoperez

3. Scala 101

4. Programming 101: Formal vs Actual
parameters

5. Scala 101: Lists of parameters

6. Scala 101: Methods are not functions

7. … but they are kind of cousins.

8. Know your implicit things

9. The compiler’s toy box: Implicit parameters
Just for methods

10. The compiler’s toy box: Implicit parameters
Just for methods

11. The compiler’s toy box: Implicit parameters
Just for methods

12. The compiler’s toy box: Implicit conversions
Conversion:
Domain = R
-10.0, 1.3, 9.2, ….
Conversion, I am
your SOURCE
TYPE
And, I am your
TARGET TYPE

13. Implicit conversions: A silly example

14. Facts
Actual implicit parameters are values.
Formal implicit parameters are all those in the implicit parameter list.
Only methods can have - a single - implicit parameter list.
Functions are values.
Guinea Pigs are pets, not food.
Implicit conversions are specially tagged functions, that is values.
Methods are not functions but can be assigned to function values thus
becoming functions so they can become implicit conversions.

15. Know your implicit context

16. The implicit context
Compound Noun (singular)
The place from where the magic unicorns come...

17. The implicit contexterror: ambiguous implicit
values:
both value c of type => C
and value d of type => C
WHY?! WHAT?!
Where did that implicit
value came from???!!!
I DONT KNOW MORTY! BUT…
RUN! RUN! RUN!

18. The implicit context is, once tamed, is...
MOSTLY HARMLESS
Implicit Context (n)
The implicit context at a given point of your source code is
the set of implicit values available for the compiler to
perform type conversions or complete function calls when
that point of code is providing an unexpected type object or
missing some parameter in a function call.
That is… a mere backpack full of values for the compiler to use.

19. Identifying the limits of your implicit context

20. Identifying the limits of your implicit context:
Scope

21. Identifying the limits of your implicit context:
Implicit parameters

22. Identifying the limits of your implicit context:
Target & goal companion objects
Conversion Source Type Target Type
A B
B A
B A

23. Patterns, let’s take it easy

24. Representing context

25. Representing context

26. Basic exercise

27. Fighting type erasure:
The compiler & implicit values to the rescue

28. Adventure time

29. Problem

30. Old-school solution
Traditional OOP
Solution

31. Type classes to the
rescue
Maintainable
+= Animal
Maintainable
+= Equipment

32. Type classes to the
rescue

33. That wasn’t just a hack...

34. A magnetic way of solving the same
problem...

35. A magnetic way of solving the same
problem...