A lecture given at the DevCon TLV conference in February 2013 (http://devcon-february.events.co.il/presentations/771-scala-best-practices): Although Scala has been gaining tremendous traction over the last couple of years, it's still a relatively new language with few "common knowledge" best- and worst-practices. This lecture will attempt to distill working knowledge from 1.5 years of production Scala use, articles from around the web and other sources into a coherent set of recommendations for those considering Scala, as well as existing practitioners.

1. Scala Best Practices
Tomer Gabel @ DevCon³
February 2013

2. • Scala is awesome
• But it’s new
• … and
misunderstood

3. We’re gonna focus on… DO’S AND DON’TS

4. Don’t

5. … overuse tuples

6. Do

8. Also

9. … did you know you can do this?

10. Don’t

11. … use null

12. Do

13. … use Option!

14. Don’t

15. … overload operators
What the hell does this mean?
s(7) <*> (s(8) <*> (s(9) ∘ add3))

16. Don’t

17. … abuse implicit parameters
def lookup( id: Int )( implicit jdbcUrl: String )
• Danger, Will Robinson!
• Primitives may be reused elsewhere
• Wrong semantics

18. Don’t

19. … abuse implicit methods, either
implicit def stringToInt( x: String ) =
x.toInt
Implicit conversion considered harmful
• Performance
• Ambiguity
• Code locality

20. Don’t

21. … over-import
import package1._
import package2._
import package3._
• Namespace pollution
• Slow compilation
• Unintended implicits

22. Do

23. … study the collection framework
• It’s a layer cake!
• Always qualify mutability
– Aim for immutability
– But have no fear
• Many gems!

24. Don’t

25. … abuse the type system
• Path-dependent types
• Visibility modifiers (e.g. package-
private)
• Case class inheritance
– Not allowed in 2.10

26. Our time is
almost up!
Questions?

27. Thank you for
listening!
Get in touch:
• http://tomergabel.com
• tomer@tomergabel.com
• @tomerg