Trait in Scala

2014/05/09 Livesense SICP倶楽部LT大会にて
ScalaのTraitについての解説

Transcript

1. 5SBJU
   JO
   4DBMB 
   -JWFTFOTF
   4*$1۞ָ෦-5େձ
   ౡ઒༔ଠ
2. 4DBMB
3. CMPHFOGSBODIJTFENJOEDPNTDBMBOPUGVODUJPOBM
4. 4DBMB
5. +BWB
6. w JOUFSGBDFͷσϑΥϧτ࣮૷
   w ϥϜμࣜ
   w ߴ֊ؔ਺
   w ܕਪ࿦ͷڧԽ
   w ฒྻੑͷڧԽʢฒྻίϨΫγϣϯɺ$PNQMFUF'VUVSFʣ
   w ஗ԆධՁ
   w 4USFBN
   w 0QUJPOBM
   w FUD IUUQXXXJOGPRDPNKQBSUJDMFTKBWBWTTDBMB IUUQOFXTNZOBWJKQTQFDJBMKBWB
7. ͦΕͰ΋4DBMB
   Λ࢖͍͍͔ͨʁ
8. ͜Μͳࢿྉ࡞Δ͘Β͍ ͔ͩΒΘ͔Γ·͢ΑͶʁ
9. ຊ೔ͷςʔϚ
   ʰτϨΠτʱ
10. ͳͥτϨΠτΛ
    ͱΓ͋͛Δ͔ʁ
11. w τϨΠτ͸4DBMBͷΦϒδΣΫτࢦ޲ݴޠͱ ͯ͠ͷϋΠϥΠτͷҰͭͩͱࢥ͏ɻ
    w "DUPS΍Β'VUVSF΍ΒΛ࢖ͬͨฒߦੑ੍ޚ ͷར఺͸ଟ͍͚Ͳɺଟ͘ͷ৬ۀϓϩάϥϚ͕ ௚໘͢Δ՝୊͸ɺ001Λ࢖ͬͨιϑτ΢ΣΞ ՝୊ͷղܾʹ͋ΔͷͰ͸ͳ͍͔ͱࢥ͏ɻ
    w ͱ͍͏͜ͱͰɺ4DBMBͷݴޠ঺հͱͯ͠τϨ Πτ͔ΒऔΓ্͛ͯΈΔɻ
12. $ scala scala> “trait”.translate(“ja_JP”) res0: List[String] = List(ಛੑ, ಛ௃, ಛ৭) IUUQFKKFXFCMJPKQDPOUFOUUSBJU
13. τϨΠτͱ͸ʁ
14. ΫϥεͷΑ͏ʹɺϝιουͱϑΟʔ ϧυͷఆٛΛΧϓηϧԽͨ͠΋ͷ Ͱɺ4DBMBʹ͓͚Δίʔυ࠶ར ༻ͷجຊ୯ҐʢίοϓຊΑΓʣ
    
15. trait Philosophical { def philosophize() { println(“զࢥ͏ނʹզ͋Γ”) } }
16. ΫϥεʹϛοΫεΠϯ w ந৅ϝϯόʔ͚ͩΛએݴͯ͠ɺϛοΫεΠϯ͢Δ ΫϥεͰͷ࣮૷Λڧ੍
    w ࣮૷Λఆٛ͢Δ͜ͱ΋Ͱ͖Δ
    w ෳ਺ͷτϨΠτΛಉ࣌ʹϛοΫεΠϯ͢Δ͜ͱ΋ Ͱ͖Δ
    w ϛοΫεΠϯͨ͠ϝιουΛΦʔόʔϥΠυͨ͠ ΓɺTVQFSݺͼग़͢͠Δ͜ͱ΋Ͱ͖Δ
17. trait A { def f() // ந৅ϝιου } ! trait B { def foo() = println("foo") } ! trait C { def bar() = println("bar") } ! class D extends A with B with C { def f() = foo() // ந৅ϝιουΛ࣮૷ˍτϨΠτBͷfooΛݺͼग़͠ override def bar() = { // τϨΠτCͷbarϝιουΛoverride super.bar() // τϨΠτCͷbarϝιουΛݺͼग़͠ println("BAR") } }
18. Πϯελϯεੜ੒࣌ʹ
    ϛοΫεΠϯ
19. class Japanese ! trait Kansai ! trait Kanto ! val me = new Japanese with Kansai with Kanto
20. TVQFSݺͼग़͠ͷઢܗԽ
21. class Animal ! trait HasLegs extends Animal ! trait FourLegged extends HasLegs ! trait Furry extends Animal ! class Cat extends Animal with Furry with FourLegged
22. "OJNBM )BT-FHT 'VSSZ 'PVS-FHHFE $BU DMBTT
    $BU
    FYUFOET
    "OJNBM
    
    
    
    
    
    XJUI
    'VSSZ
    XJUI
    'PVS-FHHFE $BU
    
    'PVS-FHHFE
    
    
    
    
    
    
    
    )BT-FHHFE
    
    'VSSZ
    
    "OJNBM
    ઢܗԽ
23. ੵΈॏͶՄೳͳมߋ
24. abstract class IntQueue { def put(x: Int) def get(): Int } ! import scala.collection.mutable.ArrayBuffer class BasicIntQueue { private val but = new ArrayBuffer[Int] def put(x: Int) = but += x def get() = but.remove(0) } ! trait Doubling extends IntQueue { abstract override def put(x: Int) = { super.put(2 * x) } } ! trait Filtering extends IntQueue { abstract override def put(x: Int) = { super.put(x.abs) } }
25. val q1 = new BasicIntQueue q1.put(10) q1.get() // Int = 10 ! val q2 = new BasicIntQueue with Doubling q2.put(10) q2.get() // Int = 20 ! val q3 = new BasicIntQueue with Doubling with Filtering q3.put(-10) q3.get() // Int = 20 ʰ4DBMBεέʔϥϒϧϓϩάϥϛϯάʱষΑΓ
26. "01ͬΆ͍͜ͱ΋Մೳ ࢀߟ
    IUUQEIBUFOBOFKQKJLP
27. trait Executor { def execute(): Unit } ! trait LoggableExecutor extends Executor { def log(() => Unit):Unit = … abstract override def execute(): Unit { log { super.execute } } } ! class SomeExecutor extends Executor { def execute(): Unit = … } ! val e = new SomeExecutor with LoggableExecutor e.execute
28. ࣗ෼ܕΞϊςʔγϣϯ
29. trait A { def foo() = “foo” } ! trait B { def bar() = “bar” } ! trait C { this: A with B => def f() = foo + bar } ! val c = new C with A with B c.f // String = foobar
30. 5SBJU
    $ͷΠϯελϯεΛੜ੒͢ Δʹ͸"ͱ#ΛϛοΫεΠϯ͠ͳ ͚Ε͹ͳΒͳ͍ɻ$͔Β"ͱ#΁ ͷґଘੑΛ໌ࣔ͢Δ͜ͱ͕Ͱ͖Δɻ
31. $BLF
    1BUUFSOͰ%*
32. class User ! trait UserRepositoryComponent { val repos: UserRepository trait UserRepository { def findById(id: Int): User } } ! class UserService { this: UserRepositoryComponent => def findById(id: Int): User = { repos.findById(id) } }
33. trait MySQLUserRepositoryComponent extends UserRepository Component { val repos = new MySQLUserRepository class MySQLUserRepository = { def findById(id: Int): User = … } } ! val userService = new UserService with MySQLUserRepositoryComponent ! val user = userService.findById(1)
34. ஫ʣDBLF
    QBUUFSO
    ʹ͍ͭͯ͸໰୊఺΋ࢦఠ ͞Ε͍ͯΔͷͰ஫ҙ
35. IUUQUPHFUUFSDPNMJ
36. ·ͱΊ
37. τϨΠτ࢖͏ͱ001͕ؾ ࣋ͪΑ͘ͳΔɻ͔΋Ͷɻ