The document discusses structuring apps in Scala and solving problems in an interesting way. It describes SoundCloud's test suite challenge which involved building a file uploader in a boring way using Flash. The speaker describes his approach using combinators and wiring, but not leveraging the type system well. He discusses Twitter and Typesafe's approaches using instance-based injection and orthogonal traits. The document outlines how SoundCloud builds apps similarly to Typesafe using components with dependencies defined through controllers. References are provided for further information.

1. Thursday, March 14, 13

2. Structuring apps in Scala
a.k.a.
I have no idea what I’m doing
phil calçado
@pcalcado
http://philcalcado.com
Scala User Group - Berlin Brandenburg
Thursday, March 14, 13

3. WHY BOTHER?
Thursday, March 14, 13

4. SOLVING INTERESTING
PROBLEMS
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5. SOLVING INTERESTING
PROBLEMS
meh.
Thursday, March 14, 13

6. SOLVING BORING
PROBLEMS IN A
INTERESTING WAY
Thursday, March 14, 13

7. SOLVING BORING
PROBLEMS IN A
INTERESTING WAY
hell yeah!
Thursday, March 14, 13

8. SOUNDCLOUD
DEVELOPER CHALLENGE’S
TEST SUITE
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9. Recruitment Challenge
W(hy)TF?
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10. Old Challenge
Build me a file uploader
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11. Old Challenge
Build me a file uploader
Boring
Thursday, March 14, 13

12. Old Challenge
Build me a file uploader
Boring
Use flash plugin
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13. Old Challenge
Build me a file uploader
Boring
Use flash plugin
Not enough code
Thursday, March 14, 13

14. New Challenge
Given a series of events
and a bunch of connected
clients, who should be
notified of which events?
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15. What I’m used to
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16. What I’m used to
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17. Combinators all the way down
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18. a LOT of code
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19. a LOT of wiring
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20. not leveraging
the type system
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21. I am pretty sure
I’m doing it wrong.
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22. TWITTER
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23. Instance-Based Injection
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24. Extremely thin, orthogonal, traits
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25. Use method visibility
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26. TYPESAFE/PRECOG
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27. Modules are abstract
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28. typesafe: self-types for
dependencies
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29. Precog: Instead of import,
extends or with
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30. SOUNDCLOUD
APPS
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31. ACTUALLY, HOW ARE WE
BUILDING APPS?
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32. internet
Legacy Application
(Rails)
Database
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33. internet
API
Sounds Users Stats Stream
Notifications Settings Recommender Messaging
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34. SOUNDCLOUD
APPS
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35. A LOT LIKE
TYPESAFE’S
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36. Controllers define dependency
on components
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37. Components are abstract
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38. One flat instance
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39. I was pretty sure
I was doing it wrong.
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40. I am pretty sure
I’m still doing it wrong.
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41. I am pretty sure
I’m still doing it wrong.
what do you use?
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42. REFERENCES
• http://bit.ly/pcalcado-goto
• http://bit.ly/effective-scala-Dependency-injection
• http://bit.ly/Bakery-from-the-Black-Lagoon
• http://bit.ly/Martin-Odersky-Reflection-and-
Compilers
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43. phil calçado
http://philcalcado.com
@pcalcado
www.soundcloud.com
Thursday, March 14, 13