Scalaリファクタリング入門「大改造！静的ビフォー・アフター」

「Better Javaの一歩先へ！ Scalaリファクタリング入門」@ビズリーチD3勉強会 第一部の資料です。

Transcript

1. େ վ ଄ ʂ ੩ త Ϗ ϑ Υ ʔ ɾ Ξ ϑ λ ʔ 
   
   
   d
   
   
   4DBMBϦϑΝΫλϦϯάೖ໳
   !UPEPLS . : ✨
2. #FUUFS
   +BWBͳίʔυ
   4DBMBΒ͠͞Λ׆͔͠ɺΑΓݎ࿚ʹ
3. ా ॴ
   ॣ ༎
   ! U P E P L S
   
   ג ࣜ ձ ࣾ Ϗ ζ Ϧ ʔ ν
   

   
   ελ ϯόΠ ࣄ ۀ ෦
   α ʔ ν ί Ξάϧ ʔϓ 

   
   
   ΢ Σ ϒΫ ϩ ʔ ϥ ʔ ͷ ։ ൃ ɾ ӡ ༻
        ೥  ݄ ೖ ࣾ
     ࡀ
    4 D B M B ྺ
    ೥  ϲ ݄
4. ͓ ࿩ ͢͠ Δ ͜ ͱ w ͳͥ#FUUFS
   +BWBͷઌͳͷ͔ʁ
   
   4DBMBΒ͠͞ͷԸܙͱ͸
   w ύλʔϯϚονͷύλʔϯ
   
   ΩϟετΛͳͯ҆͘͠શʹ
   w λϓϧΛආ͚Δ
   
   ͦͷ਺ࣈʹҙຯ͸͋Δ͔ʁ
   w 4DBMBͳྫ֎ॲཧ
   
   ੒ޭɾࣦഊΛ஋ͱͯ͠දݱ͢Δ
   w DBTF
   DMBTTʹ੍໿Λ࣋ͨͤΔ
   
   SFRVJSFͷར༻
   w TFBMFE
   USBJUͰ໢ཏੑΛ୲อ͢Δ
   
   ίϯύΠϥʹ͓ئ͍
5. ͓ ࿩ ͢͠ Δ ͜ ͱ w ͳͥ#FUUFS
   +BWBͷઌͳͷ͔ʁ
   
   4DBMBΒ͠͞ͷԸܙͱ͸
   w ύλʔϯϚονͷύλʔϯ
   
   ΩϟετΛͳͯ҆͘͠શʹ
   w λϓϧΛආ͚Δ
   
   ͦͷ਺ࣈʹҙຯ͸͋Δ͔ʁ
   w 4DBMBͳྫ֎ॲཧ
   
   ੒ޭɾࣦഊΛ஋ͱͯ͠දݱ͢Δ
   w DBTF
   DMBTTʹ੍໿Λ࣋ͨͤΔ
   
   SFRVJSFͷར༻
   w TFBMFE
   USBJUͰ໢ཏੑΛ୲อ͢Δ
   
   ίϯύΠϥʹ͓ئ͍ ˠ
   4 D B M B Λ ֶ ͼ ࢝ Ί ͨ ࠒ ͷ ࣗ ෼ ʹ 
 ɹ
   ڭ ͑ͯ ͋ ͛ ͨ ͍ ಺ ༰
6. ͳ ͥ # F U U F S
   + B W B ͷ ઌ ͳ ͷ ͔ ʁ
7. 1 def isBlank(str:String): Boolean = { 2 var strLen = 0 3 4 if(str == null || { strLen = str.length(); strLen } == 0) { 5 return true 6 } 7 8 var i = 0 9 while( i < strLen ){ 10 if(Character.isWhitespace( str.charAt(i) ) == false){ 11 return false 12 } 13 i += 1 14 } 15 16 return true 17 } # F U U F S
   + B W B ͳ ελ Πϧ
8. 1 def isBlank(str:String): Boolean = { 2 var strLen = 0 3 4 if(str == null || { strLen = str.length(); strLen } == 0) { 5 return true 6 } 7 8 var i = 0 9 while( i < strLen ){ 10 if(Character.isWhitespace( str.charAt(i) ) == false){ 11 return false 12 } 13 i += 1 14 } 15 16 return true 17 } # F U U F S
   + B W B ͳ ελ Πϧ
9. 1 def isBlank(str:String): Boolean = { 2 var strLen = 0 3 4 if(str == null || { strLen = str.length(); strLen } == 0) { 5 return true 6 } 7 8 var i = 0 9 while( i < strLen ){ 10 if(Character.isWhitespace( str.charAt(i) ) == false){ 11 return false 12 } 13 i += 1 14 } 15 16 return true 17 } # F U U F S
   + B W B ͳ ελ Πϧ ͪΐͬͱ௕͍
10. 1 def isBlank(str:String): Boolean = { 2 var strLen = 0 3 4 if(str == null || { strLen = str.length(); strLen } == 0) { 5 return true 6 } 7 8 var i = 0 9 while( i < strLen ){ 10 if(Character.isWhitespace( str.charAt(i) ) == false){ 11 return false 12 } 13 i += 1 14 } 15 16 return true 17 } # F U U F S
    + B W B ͳ ελ Πϧ ίʔυͷ௕͞ͱόάͷೖΓ΍͢͞͸
 ਖ਼ൺྫ͢ΔɻͰ͖Ε͹΋ͬͱ୹͍ͨ͘͠ɻ ͪΐͬͱ௕͍
11. 1 def isBlank(str:String): Boolean = { 2 var strLen = 0 3 4 if(str == null || { strLen = str.length(); strLen } == 0) { 5 return true 6 } 7 8 var i = 0 9 while( i < strLen ){ 10 if(Character.isWhitespace( str.charAt(i) ) == false){ 11 return false 12 } 13 i += 1 14 } 15 16 return true 17 } # F U U F S
    + B W B ͳ ελ Πϧ
12. 1 def isBlank(str:String): Boolean = { 2 var strLen = 0 3 4 if(str == null || { strLen = str.length(); strLen } == 0) { 5 return true 6 } 7 8 var i = 0 9 while( i < strLen ){ 10 if(Character.isWhitespace( str.charAt(i) ) == false){ 11 return false 12 } 13 i += 1 14 } 15 16 return true 17 } # F U U F S
    + B W B ͳ ελ Πϧ ग़ޱ͕Օॴ
13. 1 def isBlank(str:String): Boolean = { 2 var strLen = 0 3 4 if(str == null || { strLen = str.length(); strLen } == 0) { 5 return true 6 } 7 8 var i = 0 9 while( i < strLen ){ 10 if(Character.isWhitespace( str.charAt(i) ) == false){ 11 return false 12 } 13 i += 1 14 } 15 16 return true 17 } # F U U F S
    + B W B ͳ ελ Πϧ ग़ޱ͕Օॴ Ͱ͖Ε͹෼ذ͸গͳ͍΄͏͕
 γϯϓϧͰݎ࿚ɻ
14. 1 def isBlank(str:String): Boolean = { 2 var strLen = 0 3 4 if(str == null || { strLen = str.length(); strLen } == 0) { 5 return true 6 } 7 8 var i = 0 9 while( i < strLen ){ 10 if(Character.isWhitespace( str.charAt(i) ) == false){ 11 return false 12 } 13 i += 1 14 } 15 16 return true 17 } # F U U F S
    + B W B ͳ ελ Πϧ
15. 1 def isBlank(str:String): Boolean = { 2 var strLen = 0 3 4 if(str == null || { strLen = str.length(); strLen } == 0) { 5 return true 6 } 7 8 var i = 0 9 while( i < strLen ){ 10 if(Character.isWhitespace( str.charAt(i) ) == false){ 11 return false 12 } 13 i += 1 14 } 15 16 return true 17 } # F U U F S
    + B W B ͳ ελ Πϧ ࠶୅ೖՄೳͳม਺
16. 1 def isBlank(str:String): Boolean = { 2 var strLen = 0 3 4 if(str == null || { strLen = str.length(); strLen } == 0) { 5 return true 6 } 7 8 var i = 0 9 while( i < strLen ){ 10 if(Character.isWhitespace( str.charAt(i) ) == false){ 11 return false 12 } 13 i += 1 14 } 15 16 return true 17 } # F U U F S
    + B W B ͳ ελ Πϧ ࠶୅ೖՄೳͳม਺ ࠶୅ೖՄೳʮঢ়ଶʯΛ࣋ͭͱ͍͏͜ͱɻ
 ঢ়ଶΛؾʹ͢Δඞཁ͕͋Δɻ
17. 1 def isBlank(str: String): Boolean = 2 Option(str).fold(true)(_.forall(Character.isWhitespace)) 4 D B M B Β ͠ ͍ ελ Πϧ
18. 1 def isBlank(str: String): Boolean = 2 Option(str).fold(true)(_.forall(Character.isWhitespace)) w ୹͘ಡΈ΍͘͢
    w ෼ذ͕গͳ͘
    w ঢ়ଶΛؾʹ͢Δඞཁͳ͘ 4 D B M B Β ͠ ͍ ελ Πϧ
19. 1 def isBlank(str: String): Boolean = 2 Option(str).fold(true)(_.forall(Character.isWhitespace)) w ୹͘ಡΈ΍͘͢
    w ෼ذ͕গͳ͘
    w ঢ়ଶΛؾʹ͢Δඞཁͳ͘ 4 D B M B Β ͠ ͍ ελ Πϧ ☺ όάͷࠞೖͷՄೳੑ͕Լ͕Δ
20. ύ λ ʔϯ Ϛ ο ν ͷ ύ λ ʔϯ
21. 0 Q U J P O ͷ ύ λ ʔϯ Ϛ ο ν 1 option match { 2 case Some(x) => println(s"$x is here!") 3 case None => println("oh…") 4 }
22. γ ʔ έ ϯε ͷ ύ λ ʔϯ Ϛ ο ν 1 List("Noel", "Liam", "Gem", "Andy", "Alan") match { 2 case List(_, second, _*) => println(s"Hello $second!") 3 case _ => 4 } 5 // => Hello Liam!
23. ί ϯε τ ϥ Ϋ λύ λ ʔϯ 1 val user = User("Martin", Place("Tokyo", "Shibuya")) 2 3 user match { 4 case User(name, Place(pref, _)) => "$name in $pref" 5 case _ => 6 } 7 // => Martin lives in Tokyo!
24. ܕ ν Σ ο Ϋ ͱ Ω ϟε τ 1 def count2x(x: Any): Int = { 2 if (x.isInstanceOf[String]) { 3 x.asInstanceOf[String].length * 2 4 } else if (x.isInstanceOf[Int]) { 5 x.asInstanceOf[Int] * 2 6 } else -1 7 } 8 9 count2x("scala") // 10 10 count2x(7) // 14
25. ܕ ν Σ ο Ϋ ͱ Ω ϟε τ 1 def count2x(x: Any): Int = { 2 if (x.isInstanceOf[String]) { 3 x.asInstanceOf[String].length * 2 4 } else if (x.isInstanceOf[Int]) { 5 x.asInstanceOf[Int] * 2 6 } else -1 7 } 8 9 count2x("scala") // 10 10 count2x(7) // 14 ܕνΣοΫ
26. ܕ ν Σ ο Ϋ ͱ Ω ϟε τ 1 def count2x(x: Any): Int = { 2 if (x.isInstanceOf[String]) { 3 x.asInstanceOf[String].length * 2 4 } else if (x.isInstanceOf[Int]) { 5 x.asInstanceOf[Int] * 2 6 } else -1 7 } 8 9 count2x("scala") // 10 10 count2x(7) // 14 Ωϟετ
27. ܕ ν Σ ο Ϋ ͱ Ω ϟε τ 1 def count2x(x: Any): Int = { 2 if (x.isInstanceOf[String]) { 3 x.asInstanceOf[String].length * 2 4 } else if (x.isInstanceOf[Int]) { 5 x.asInstanceOf[Int] * 2 6 } else -1 7 } 8 9 count2x("scala") // 10 10 count2x(7) // 14 Ωϟετ গ͠৑௕ɻ
    Θ͟Θ͟Ωϟετ͢Δͷ΋ةݥͳ߳Γɻ ܕνΣοΫ
28. ܕ ෇ ͖ ύ λ ʔϯ 1 def count2x(x: Any): Int = x match { 2 case x:String => x.length * 2 3 case x: Int => x * 2 4 case _ => -1 5 } 6 7 count2x("scala") // 10 8 count2x(7) // 14
29. ܕ ෇ ͖ ύ λ ʔϯ 1 def count2x(x: Any): Int = x match { 2 case x:String => x.length * 2 3 case x: Int => x * 2 4 case _ => -1 5 } 6 7 count2x("scala") // 10 8 count2x(7) // 14 ☺ ίʔυͷݟ௨͕͠޲্ɻ
 Ωϟετ΋ෆཁͰ҆৺ɻ
30. ܕ ফ ڈ ʹ ஫ ҙ 1 def detectType(x: Any): String = x match { 2 case x: List[Int] => "This is List of Int!" 3 case _ => "What?" 4 } 5 6 detectType(List("string!")) // => This is List of Int!
31. ܕ ফ ڈ ʹ ஫ ҙ 1 def detectType(x: Any): String = x match { 2 case x: List[Int] => "This is List of Int!" 3 case _ => "What?" 4 } 5 6 detectType(List("string!")) // => This is List of Int! +BWBͱಉ༷ɺίϨΫγϣϯͷཁૉܕͷ৘ใ͸
 ࣮ߦ࣌ʹ͸؅ཧ͞Εͳ͍ ˞"SSBZΛআ͘
32. λ ϓϧ Λ ආ ͚ Δ
33. λ ϓϧ 1 // ঎඼ 2 case class Item(name: String, price: Int) 3 4 // ঎඼ͷ੫ࠐՁ֨ͱՁ֨ϥϕϧΛฦ͢
    5 def labelPriceWithTax(item: Item): (Int, String) = { 6 val withTax = item.price * 1.08 7 val label = s"ܹ҆େಛՁ ¥${item.price}ʢ੫ࠐʣ" 8 (withTax, label) 9 }
34. λ ϓϧ 1 // ঎඼ 2 case class Item(name: String, price: Int) 3 4 // ঎඼ͷ੫ࠐՁ֨ͱՁ֨ϥϕϧΛฦ͢
    5 def labelPriceWithTax(item: Item): (Int, String) = { 6 val withTax = item.price * 1.08 7 val label = s"ܹ҆େಛՁ ¥${item.price}ʢ੫ࠐʣ" 8 (withTax, label) 9 } ☺ +BWBͰ͸-JTU0CKFDUͷΑ͏ʹฦ͍ͯͨ͠΋ͷ͕
 ܕͷ৘ใΛΩʔϓͨ͠··ฦͤͯ҆৺
35. Ξ ϯ νύ λ ʔϯ 
    Ξ ϯ μʔε ί Ξ Ͱ ͷ ΞΫ η ε 1 val apple = Item("αϯ;͡", 158) 2 val x = labelPriceWithTax(apple) 3 println(s"${x._1}͕ͳΜͱ${x._2}!") 4 // αϯ;͕͡ͳΜͱܹ҆େಛՁ ¥158!
36. Ξ ϯ νύ λ ʔϯ 
    Ξ ϯ μʔε ί Ξ Ͱ ͷ ΞΫ η ε 1 val apple = Item("αϯ;͡", 158) 2 val x = labelPriceWithTax(apple) 3 println(s"${x._1}͕ͳΜͱ${x._2}!") 4 // αϯ;͕͡ͳΜͱܹ҆େಛՁ ¥158! ʮY@ʯͷͳͲͷ਺ࣈ͸
 ཁૉʹ͍ͭͯͷ৘ใΛԿ΋఻͍͑ͯͳ͍ɻ
 औΓҧ͑ͯ΋ؾ͖ͮͮΒ͍ɻ
    
37. վ ળ ྫ  
    ม ਺ ୅ ೖ ࣌ ʹ λ ϓϧ Λ ෼ ղ 1 val apple = Item("αϯ;͡", 158) 2 val (name, priceLabel) = labelPriceWithTax(apple) 3 println(s"${name}͕ͳΜͱ${priceLabel}!") 4 // αϯ;͕͡ͳΜͱܹ҆େಛՁ ¥158! ҙຯͷ͋Δม਺໊ͰΞΫηεͰ͖ͯ҆৺
 ม਺͕૿͑ͯ΋औΓҧ͑ʹ͍͘ ☺
38. վ ળ ྫ  
    ύ λ ʔϯ Ϛ ο ν Ͱ λ ϓϧ Λ ෼ ղ 1 val apple = Item("αϯ;͡", 158) 2 labelPriceWithTax(apple) match { case (name, price) => 3 println(s"${name}͕ͳΜͱ${price}!") 4 } 5 // αϯ;͕͡ͳΜͱܹ҆େಛՁ ¥158!
39. 4 D B M B ͳ ྫ ֎ ॲ ཧ
40. ྫ ֎ ॲ ཧ 1 // ྫ֎Λ౤͛ΔՄೳੑͷ͋Δϝιου 2 def detect(bytes: Array[Byte]): Charset = { 3 val detectedCharsetName: String = ... 4 Charset.forName(detectedCharsetName) 5 } 6 7 // ϝιουͷݺͼग़͠ݩͰྫ֎ॲཧ 8 try { 9 detect(bytes) 10 ... 11 } catch { 12 case e: Exception => ... 13 }
41. ྫ ֎ ॲ ཧ 1 // ྫ֎Λ౤͛ΔՄೳੑͷ͋Δϝιου 2 def detect(bytes: Array[Byte]): Charset = { 3 val detectedCharsetName: String = ... 4 Charset.forName(detectedCharsetName) 5 } 6 7 // ϝιουͷݺͼग़͠ݩͰྫ֎ॲཧ 8 try { 9 detect(bytes) 10 ... 11 } catch { 12 case e: Exception => ... 13 } ੒ޭ
    PS
    ࣦഊΛ஋ͱͯ͠ѻ͍ɺ
 ੍ޚϑϩʔΛγϯϓϧʹ͍ͨ͠
    
42. ྫ ֎ Ͱ ͸ ͳ ͘ ʜ ੒ޭ
    PS
    ࣦഊΛදݱ͢Δܕͱͦͷ஋Λ༻͍Δ
    w 0QUJPO< 5>
 ੒ޭ࣌ͷ஋Λ4PNFɺ
    ࣦഊΛ/POFͰදݱ
    w &JUIFS< "
    #>
 ੒ޭ࣌ͷ৘ใΛ3JHIUͰɺࣦഊͷ৘ใΛ-FGUͰදݱ
    w 5SZ< 5>
 ྫ֎Λ౤͛ΔՄೳੑͷ͋ΔॲཧΛந৅Խɺ4VDDFTTͱ'BJMVSFͰ݁ՌΛදݱ
43. 0 Q U J P O ܕ w 4PNFͱ/POFͱ͍͏छྨ
    w ஋͕ଘࡏ͢Δ͜ͱΛද͢4PNF W
    w ஋͕ଘࡏ͠ͳ͍͜ͱΛද͢/POF
    w 0QUJPOܕ
    ˠ
    ʮ஋͕ଘࡏ͠ͳ͍Մೳੑ͕͋Δʯͱ͍͏ϝοηʔδ
44. 0 Q U J P O Ͱ ੒ ޭ  ࣦ ഊ Λ ද ݱ ͢ Δ 1 // try / catchͰOptionΛฦ͢ 2 def detect(bytes: Array[Byte]): Option[Charset] = { 3 val detectedCharsetName: String = ... 4 try { 5 Some(Charset.forName(detectedCharsetName)) 6 } catch { 7 case e: Exception => None 8 } 9 } ੒ޭ࣌͸4PNFɺࣦഊ࣌͸/POFͰฦ͢
45. 0 Q U J P O Ͱ ੒ ޭ  ࣦ ഊ Λ ද ݱ ͢ Δ 1 // ࣦഊͨ͠ΒσϑΥϧτ஋Λ࢖͏ 2 detect(bytes).getOrElse(Charset.defaultCharset) 3 4 // ࣦഊͨ͠ΒԿ΋͠ͳ͍ 5 detect(bytes).map { charset => 6 // Կ͔ॲཧ 7 } ݺͿଆͰͷѻ͍ ݁ՌʹԠͨ͡ॲཧ͕҆શ͔ͭॊೈʹͰ͖Δ ☺
46. & J U I F S ܕ w 3JHIU D ͱ-FGU F ͱ͍͏छྨ
    w 3JHIU͸ʮਖ਼͍͠ʯʹ͔͚ͯ੒ޭ࣌ͷ஋Λ֨ೲ͢Δͷ͕ओྲྀ
    w -FGU΋஋Λ࣋ͯΔͷͰɺࣦഊ࣌ͷ৘ใΛ֨ೲͰ͖Δ
    w &JUIFSܕ
    ˠ
    ʮࣦഊ͢ΔՄೳੑ͕͋Δʯͱ͍͏ϝοηʔδ
47. & J U I F S Ͱ ੒ ޭ  ࣦ ഊ Λ ද ݱ ͢ Δ 1 // try / catchͰOptionΛฦ͢ 2 def detect(bytes: Array[Byte]): Either[Exception, Charset] = { 3 val detectedCharsetName: String = ... 4 try { 5 Right(Charset.forName(detectedCharsetName)) 6 } catch { 7 case e: Exception => Left(e) 8 } 9 } ੒ޭ࣌͸3JHIUɺࣦഊ࣌͸-FGUͰฦ͢
48. & J U I F S Ͱ ੒ ޭ  ࣦ ഊ Λ ද ݱ ͢ Δ 1 // 2 val charset = detect(bytes) match { 3 case Right(charset) => charset 4 case Left(e) => 5 logger.error(s"Oops! :$e") 6 Charset.defaultCharset 7 } ݺͿଆͰͷѻ͍ ݺͼग़͢ਓʹ݁ՌͷνΣοΫΛڧ੍Ͱ͖Δ
 ࣦഊ࣌ͷ৘ใ͕࣋ͯΔͷͰϩάʹग़ͨ͠ΓͳͲ ☺
49. 5S Z ܕ w 4VDDFTT W ͱ'BJMVSF F ͱ͍͏छྨ
    w 4VDDFTT W ʹ੒ޭ࣌ͷ஋
    w 'BJMVSF F ʹࣦഊ࣌ͷ৘ใ
    w ྫ֎͕౤͛ΒΕΔ͔΋͠Εͳ͍ॲཧΛ5SZͰғΉ͚ͩͰ0,
    w 5SZܕ
    ˠ
    ʮࣦഊ͢ΔՄೳੑ͕͋Δʯͱ͍͏ϝοηʔδ
50. 5S Z Ͱ ੒ ޭ  ࣦ ഊ Λ ද ݱ ͢ Δ 1 // ݁ՌΛTryͰड͚औΔ 2 import scala.util.Try 3 def detect(bytes: Array[Byte]): Try[Charset] = { 4 val detectedCharsetName: String = ... 5 Try(Charset.forName(ud.getDetectedCharset)) 6 } 7 ࣦഊ͢Δ͔΋͠Εͳ͍ॲཧΛ5SZ ͰแΉ
51. 5S Z Ͱ ੒ ޭ  ࣦ ഊ Λ ද ݱ ͢ Δ 1 // 2 val charset = detect(bytes) match { 3 case Success(charset) => charset 4 case Failure(e) => 5 logger.error(s"Oops! :$e") 6 Charset.defaultCharset 7 } ݺͿଆͰͷѻ͍ 4VDDFTT'BJMVSFͰύλʔϯϚον ☺
52. ' B J M V S F ʹ ͳ Δ ͷ ͸ / P O ' B U B M ͳ ΋ ͷ • VirtualMachineError • ThreadDeath • InterruptedException • LinkageError • ControlThrowable 'BUBMͳΤϥʔɾྫ֎͸ͦͷ··εϩʔ͞ΕΔ
53. 5S Z ͱ G P S ࣜ 1 // ྫ֎Λى͔͜͢΋͠Εͳ͍ϝιου 2 def someMethod: Int = ??? 3 def anotherMethod: Int = ???
54. 5S Z ͱ G P S ࣜ 1 // TryΛforࣜͰ߹੒͢Δ 2 val result = for { 3 result1 <- Try(someMethod) 4 result2 <- Try(anotherMethod) 5 } yield result1 + result2 6 7 result match { 8 case Success(result) => println(result) 9 case Failure(e) => println(s"Opps: ", e) 10 }
55. 5S Z ͱ G P S ࣜ 1 // TryΛforࣜͰ߹੒͢Δ 2 val result = for { 3 result1 <- Try(someMethod) 4 result2 <- Try(anotherMethod) 5 } yield result1 + result2 6 7 result match { 8 case Success(result) => println(result) 9 case Failure(e) => println(s"Opps: ", e) 10 } ʮ"ͱ#͕྆ํ੒ޭͨ͠ͱ͖ͷΈ9͢Δʯ

    
    ͳͲ͕෼͔Γ΍͘͢දݱͰ͖Δ ☺
56. D B T F
    D M B T T ʹ ੍ ໿ Λ ࣋ ͨ ͤ Δ
57. Ұ ݟ ͳ Μ ͷ ม ఩ ΋ ͳ ͍ D B T F
    D M B T T 1 case class Person( 2 name: String, 3 age: Int 4 )
58. Ұ ݟ ͳ Μ ͷ ม ఩ ΋ ͳ ͍ D B T F
    D M B T T 1 case class Person( 2 name: String, 3 age: Int 4 ) ࡀͱ͔͸ͳ͍ΑͶɻ
 Ҿ਺ΛνΣοΫ͠ͳ͖Όɻ
59. 1 case class Person( 2 name: String, 3 age: Int 4 ) { 5 if(age < 0) throw new IllegalArgumentException("Age must be natural!") 6 } ੍ ໿ Λ ΋ ͨ ͤ ͨ D B T F
    D M B T T
60. 1 case class Person( 2 name: String, 3 age: Int 4 ) { 5 if(age < 0) throw new IllegalArgumentException("Age must be natural!") 6 } ੍ ໿ Λ ΋ ͨ ͤ ͨ D B T F
    D M B T T ࣄલ৚݅Ͱ͋Δ͜ͱΛ
 ΋ͬͱ໌֬ʹ఻͍͑ͨ
61. 1 case class Person( 2 name: String, 3 age: Int 4 ) { 5 require(age >= 0, "Age must be natural number!") 6 } ੍ ໿ Λ ΋ ͨ ͤ ͨ D B T F
    D M B T T
62. 1 case class Person( 2 name: String, 3 age: Int 4 ) { 5 require(age >= 0, "Age must be natural number!") 6 } ੍ ໿ Λ ΋ ͨ ͤ ͨ D B T F
    D M B T T ࣄલ৚݅
63. 1 case class Person( 2 name: String, 3 age: Int 4 ) { 5 require(age >= 0, "Age must be natural number!") 6 } ੍ ໿ Λ ΋ ͨ ͤ ͨ D B T F
    D M B T T ࣄલ৚݅Λຬͨ͞ͳ͍৔߹ͷ
 Τϥʔϝοηʔδ
64. 1 case class Person( 2 name: String, 3 age: Int 4 ) { 5 require(age >= 0, "Age must be natural number!") 6 } ੍ ໿ Λ ΋ ͨ ͤ ͨ D B T F
    D M B T T 1 val joe = Person("Joe Cool", -2))
65. 1 case class Person( 2 name: String, 3 age: Int 4 ) { 5 require(age >= 0, "Age must be natural number!") 6 } ੍ ໿ Λ ΋ ͨ ͤ ͨ D B T F
    D M B T T 1 val joe = Person("Joe Cool", -2)) 2 // => java.lang.IllegalArgumentException: requirement failed: Age must be natural number!
66. 1 case class Person( 2 name: String, 3 age: Int 4 ) { 5 require(age >= 0, "Age must be natural number!") 6 } ੍ ໿ Λ ΋ ͨ ͤ ͨ D B T F
    D M B T T &JUIFS΍5SZͱ૊Έ߹ΘͤΔͱ͏Ε͍͠ ☺ 1 val joe = Person("Joe Cool", -2)) 2 // => java.lang.IllegalArgumentException: requirement failed: Age must be natural number!
67. T F B M F E
    U S B J U Ͱ ໢ ཏ ੑ Λ ୲ อ ͢ Δ
68. Ϣ ʔ β ʔϓ ϥ ϯ Λ ύ λ ʔϯ Ϛ ο ν 1 case class User(name: String, age: Int)
69. Ϣ ʔ β ʔϓ ϥ ϯ Λ ύ λ ʔϯ Ϛ ο ν 1 case class User(name: String, age: Int) 2 3 trait Plan 4 case class Free(user: User) extends Plan // ແྉϓϥϯ 5 case class Premium(user: User) extends Plan // ϓϨϛΞϜϓϥϯ
70. Ϣ ʔ β ʔϓ ϥ ϯ Λ ύ λ ʔϯ Ϛ ο ν 1 case class User(name: String, age: Int) 2 3 trait Plan 4 case class Free(user: User) extends Plan // ແྉϓϥϯ 5 case class Premium(user: User) extends Plan // ϓϨϛΞϜϓϥϯ 6 7 val userA = Free(User("Taro", 23)) 8 val userB = Premium(User("Jiro", 25)) 9
71. Ϣ ʔ β ʔϓ ϥ ϯ Λ ύ λ ʔϯ Ϛ ο ν 1 case class User(name: String, age: Int) 2 3 trait Plan 4 case class Free(user: User) extends Plan // ແྉϓϥϯ 5 case class Premium(user: User) extends Plan // ϓϨϛΞϜϓϥϯ 6 7 val userA = Free(User("Taro", 23)) 8 val userB = Premium(User("Jiro", 25)) 9 10 userB match { 11 case Free(User(name, _)) => println(s"Hi, $name.") 12 case Premium(User(name, _)) => println(s"Hello, $name!") 13 }
72. Ϣ ʔ β ʔϓ ϥ ϯ Λ ύ λ ʔϯ Ϛ ο ν 1 case class User(name: String, age: Int) 2 3 trait Plan 4 case class Free(user: User) extends Plan // ແྉϓϥϯ 5 case class Premium(user: User) extends Plan // ϓϨϛΞϜϓϥϯ 6 7 val userA = Free(User("Taro", 23)) 8 val userB = Premium(User("Jiro", 25)) 9 10 userB match { 11 case Free(User(name, _)) => println(s"Hi, $name.") 12 case Premium(User(name, _)) => println(s"Hello, $name!") 13 } 14 // => Hello, Jiro!
73. ϓ ϥ ϯ Λ ૿ ΍ ͢ 1 case class User(name: String, age: Int) 2 3 trait Plan 4 case class Free(user: User) extends Plan 5 case class Premium(user: User) extends Plan
74. ϓ ϥ ϯ Λ ૿ ΍ ͢ 1 case class User(name: String, age: Int) 2 3 trait Plan 4 case class Free(user: User) extends Plan 5 case class Premium(user: User) extends Plan 6 case class Campaign(user: User) extends Plan 7 8 val userA = Free(User("Taro", 23)) 9 val userB = Premium(User("Jiro", 25)) 10 val userC = Campaign(User("Saburo", 28))
75. ϓ ϥ ϯ Λ ૿ ΍ ͢ 1 case class User(name: String, age: Int) 2 3 trait Plan 4 case class Free(user: User) extends Plan 5 case class Premium(user: User) extends Plan 6 case class Campaign(user: User) extends Plan 7 8 val userA = Free(User("Taro", 23)) 9 val userB = Premium(User("Jiro", 25)) 10 val userC = Campaign(User("Saburo", 28)) 11 12 Seq(userA, userB, userC) foreach { 13 case Free(User(name, _)) => println(s"Hi, $name.") 14 case Premium(User(name, _)) => println(s"Hello, $name!") 15 }
76. ϓ ϥ ϯ Λ ૿ ΍ ͢ 1 case class User(name: String, age: Int) 2 3 trait Plan 4 case class Free(user: User) extends Plan 5 case class Premium(user: User) extends Plan 6 case class Campaign(user: User) extends Plan 7 8 val userA = Free(User("Taro", 23)) 9 val userB = Premium(User("Jiro", 25)) 10 val userC = Campaign(User("Saburo", 28)) 11 12 Seq(userA, userB, userC) foreach { 13 case Free(User(name, _)) => println(s"Hi, $name.") 14 case Premium(User(name, _)) => println(s"Hello, $name!") 15 } 16 // => Hi, Taro. 17 // => Hello, Jiro! 18 // => scala.MatchError: Campaign(User(Saburo,28)) …
77. ϓ ϥ ϯ Λ ૿ ΍ ͢ 1 case class User(name: String, age: Int) 2 3 trait Plan 4 case class Free(user: User) extends Plan 5 case class Premium(user: User) extends Plan 6 case class Campaign(user: User) extends Plan 7 8 val userA = Free(User("Taro", 23)) 9 val userB = Premium(User("Jiro", 25)) 10 val userC = Campaign(User("Saburo", 28)) 11 12 Seq(userA, userB, userC) foreach { 13 case Free(User(name, _)) => println(s"Hi, $name.") 14 case Premium(User(name, _)) => println(s"Hello, $name!") 15 } 16 // => Hi, Taro. 17 // => Hello, Jiro! 18 // => scala.MatchError: Campaign(User(Saburo,28)) … .BUDI&SSPS͸࣮ߦ࣌Τϥʔɻ
 ࣮ߦલʹύλʔϯͷ࿙Εʹؾ͖͍ͮͨ
78. 4 F B M F E म ০ ࢠ Ͱ ໢ ཏ ੑ Λ ୲ อ ͢ Δ 1 case class User(name: String, age: Int) 2 3 trait Plan
79. 4 F B M F E म ০ ࢠ Ͱ ໢ ཏ ੑ Λ ୲ อ ͢ Δ 1 case class User(name: String, age: Int) 2 3 sealed trait Plan
80. 4 F B M F E म ০ ࢠ Ͱ ໢ ཏ ੑ Λ ୲ อ ͢ Δ 1 case class User(name: String, age: Int) 2 3 sealed trait Plan w ಉ͡ϑΝΠϧ಺Ͱ͸ܧঝՄೳ
    w ผͷϑΝΠϧ͔Β͸ܧঝෆՄ
81. 4 F B M F E म ০ ࢠ Ͱ ໢ ཏ ੑ Λ ୲ อ ͢ Δ 1 case class User(name: String, age: Int) 2 3 sealed trait Plan w ಉ͡ϑΝΠϧ಺Ͱ͸ܧঝՄೳ
    w ผͷϑΝΠϧ͔Β͸ܧঝෆՄ ͜ͷϑΝΠϧ಺Ͱఆٛ͞Εͨ΋ͷҎ֎ʹ
 1MBO͸ଘࡏ͠ͳ͍͜ͱ͕อূ͞ΕΔ
82. 4 F B M F E म ০ ࢠ Ͱ ໢ ཏ ੑ Λ ୲ อ ͢ Δ 1 case class User(name: String, age: Int) 2 3 sealed trait Plan 4 case class Free(user: User) extends Plan 5 case class Premium(user: User) extends Plan 6 case class Campaign(user: User) extends Plan 7 8 val userA = Free(User("Taro", 23)) 9 val userB = Premium(User("Jiro", 25)) 10 val userC = Campaign(User("Saburo", 28)) 11 12 Seq(userA, userB, userC) foreach { 13 case Free(User(name, _)) => println(s"Hi, $name.") 14 case Premium(User(name, _)) => println(s"Hello, $name!") 15 }
83. [warn] It would fail on the following input: Campaign(_) [warn] Seq(userA, userB, userC) foreach { [warn] ^ [warn] one warning found 4 F B M F E म ০ ࢠ Ͱ ໢ ཏ ੑ Λ ୲ อ ͢ Δ ίϯύΠϧ͢Δͱʜ ʮ$BNQBJHO͕དྷͨΒམͪΔ΍Ͱʂʯͱ
    
    
    ίϯύΠϥ͕ڭ͑ͯ͘ΕΔ ☺
84. [warn] It would fail on the following input: Campaign(_) [warn] Seq(userA, userB, userC) foreach { [warn] ^ [warn] one warning found 4 F B M F E म ০ ࢠ Ͱ ໢ ཏ ੑ Λ ୲ อ ͢ Δ ίϯύΠϧ͢Δͱʜ ʮ$BNQBJHO͕དྷͨΒམͪΔ΍Ͱʂʯͱ
    
    
    ίϯύΠϥ͕ڭ͑ͯ͘ΕΔ ☺ 8BSOJOHແࢹ͠ͳ͍ͰͶ ☺
85. ͓ ࿩ ͠ ͠ ͨ ͜ ͱ w ͳͥ#FUUFS
    +BWBͷઌͳͷ͔ʁ
    w ύλʔϯϚονͷύλʔϯ
    w λϓϧΛආ͚Δ
    w 4DBMBͳྫ֎ॲཧ
    w DBTF
    DMBTTʹ੍໿Λ࣋ͨͤΔ
    w TFBMFE
    USBJUͰ໢ཏੑΛ୲อ͢Δ
86. ) B W F
    B
    ( P P E
    4 D B M B
    - J G F  . : ✨