ScalaでつくるInvalid stateのない世界

Transcript

1. 4DBMBͰͭ͘Δ
   *OWBMJE
   TUBUFͷͳ͍ੈք :"1$"TJB
   )BDIJPKJ
   
   NJE
   JO
   4IJOBHBXB
   TU
   EBZ
2. ࣗݾ঺հ ͨͬ͘ΜʢUBLLLVOʣ
   ͲͷαʔϏεͰ΋େମ͜ͷ໊લ
   4DBMB
   3VCZ
   &SMBOH
3. ࠓճ͸Կͷ࿩ʁ 4DBMBͰͭ͘Δ
   *OWBMJE
   TUBUFͷͳ͍ੈք
4. ࠓճ͸Կͷ࿩ʁ 4DBMBͰͭ͘Δ
   *OWBMJE
   TUBUFͷͳ͍ੈք ˣ
   όϦσʔγϣϯͷ͓࿩
5. ࠓճ͸Կͷ࿩ʁ 4DBMBͰͭ͘Δ
   *OWBMJE
   TUBUFͷͳ͍ੈք ˣ
   όϦσʔγϣϯͷ͓࿩ όϦσʔγϣϯʹࣦഊͨ͠ঢ়ଶΛࢦ͢
   
6. ൃදʹࢸͬͨܦҢ w ීஈ4DBMBͰΞϓϦέʔγϣϯΞʔΩςΫνϟ͔ Βݕ౼ͭͭ͠։ൃ
   w ΦϒδΣΫτͷόϦσʔγϣϯʹؔͯ͠΋݁ߏ಄ Λ೧Δ͜ͱ͕͋ͬͨ
   w ࢼߦࡨޡ͍ͯͨ͠Βྑ͍ײ͡ͷ͕ग़དྷͨ
   w ౰࣌ʮϠύνʔ΍Δͧʂʯͱ͍͏੠
7. ͳΒ࿩ͦ͏ʂ
8. ΦϒδΣΫτΛόϦσʔγϣϯ͢Δ w ͱ͋ΔΦϒδΣΫτ͕͋Δ
   w ͦͷΦϒδΣΫτ͸ͻͱͭͳ͍͠͸ෳ਺ͷϑΟʔ ϧυΛ࣋ͭ
   w ͦͷϑΟʔϧυͷ಺༰೗ԿͰΦϒδΣΫτࣗମ ͷ༗ޮແޮΛܾఆ͢Δ
9. class Person < ActiveRecord::Base validates :name, { presence: true } validates :age, { presence: true, numericality: {greater_than_or_equal_to: 0} } end person = Person.new(name: "takkkun", age: -1) if (person.invalid?) { # handle person.errors } ΦϒδΣΫτΛόϦσʔγϣϯ͢Δ "DUJWF3FDPSEͷྫ
10. ΦϒδΣΫτΛόϦσʔγϣϯ͢Δ 4DBMBͷྫ class Person(val name: String, val age: Int) { def validate(): List[String] = { var errors: List[String] = List.empty if (name.isEmpty) { errors :+= "name cannot be blank" } if (age < 0) { errors :+= "age must be zero or a positive number" } errors } def isValid(): Boolean = validate().isEmpty }
11. ѻ͏ଆ͕όϦσʔγϣϯ࣮ߦͷ੹೚Λ࣋ͭ val person = new Person("takkkun", -1) if (!person.isValid) { val errors = person.validate() // handle errors } ѻ͏ଆ͕όϦσʔγϣϯΛݺͼग़͠ɺؾʹ͔͚Δඞཁ͕͋Δ
    val person = new Person("takkkun", -1) // handle person όϦσʔγϣϯΛݺͼग़͞ͳ͍ϛε΋ى͜ΓಘΔ
    def handlePerson(person: Person) { if (person.isValid) { // handle person } } ؔ਺ͳͲͰڥքΛ·͍ͨͩ৔߹΋ؾʹ͔͚Δඞཁ͕͋Δ
    
12. ΊΜͲ͍͘͞ʂ
13. w ͜ͷΞϓϩʔν͸ʮΦϒδΣΫτ͕༗ޮແޮͱ ͍͏ঢ়ଶʯΛ࣋ͭ
    w ঢ়ଶΛ࣋ͭҎ্ؾʹ͔͚Δඞཁ͕͋Δ
    w ·ͨɺ༗ޮແޮҎ֎ʹ΋ঢ়ଶΛ࣋ͭ͜ͱ͸ߟ͑ ΒΕΔ
    w ͍ΖΜͳঢ়ଶ͕૊Έ߹Θ͞Δͱʜʜ ʮঢ়ଶʯ͸ةݥͳݴ༿
14. ΊΜͲ͍͘͞ʂʂ
15. ʮৗʹ༗ޮʯͱ͍͏ߟ͑ํ w ʮΦϒδΣΫτ͕༗ޮແޮͰ͋Δͱ͍͏ঢ়ଶʯ ͕अຐͳΒແͯ͘͠͠·͓͏
    w ͢ͳΘͪʮৗʹ༗ޮʯ
    w ͜ͷΞϓϩʔνࣗମ͸௝͍͠Θ͚Ͱ΋ͳ͍
    ʢྫ
    ೔࣌ΫϥεͳͲʣ
16. ʮৗʹ༗ޮʯͱ͍͏ߟ͑ํ w %%%ͷจ຺ʹ͓͚ΔΤϯςΟςΟͰɺʮৗʹ༗ ޮͳΤϯςΟςΟʯͱͯ͠l"MXBZT
    WBMJE
    FOUJUZz ͱ͍͏ݴ༿͕࢖ΘΕ͍ͯΔ
    w ͦΕʹͳΒ͍ʮৗʹ༗ޮʯ͸l"MXBZT
    WBMJEzͱশ ͢Δ
17. "MXBZT
    WBMJE
    
    *OWBMJE
    TUBUF͕ͳ͍
18. 4DBMBͰͭ͘Δ
    *OWBMJE
    TUBUFͷͳ͍ੈք
19. ͪͳΈʹ "MXBZT
    WBMJEΛ൷൑͢Δߟ͑ํ΋͋Δ
    IUUQKF⒎SFZQBMFSNPDPNCMPHUIFGBMMBDZPG UIFBMXBZTWBMJEFOUJUZ
20. class Person(val name: String, val age: Int) { var errors: List[String] = List.empty if (name.isEmpty) { errors :+= "name cannot be blank" } if (age < 0) { errors :+= "age must be zero or a positive number" } if (errors.nonEmpty) { throw new Exception(errors.mkString(", ")) } } 4DBMBͰ"MXBZT
    WBMJEΛ࣮ݱ͢Δ
21. class Person(val name: String, val age: Int) { var errors: List[String] = List.empty if (name.isEmpty) { errors :+= "name cannot be blank" } if (age < 0) { errors :+= "age must be zero or a positive number" } if (errors.nonEmpty) { throw new Exception(errors.mkString(", ")) } } 4DBMBͰ"MXBZT
    WBMJEΛ࣮ݱ͢Δ όϦσʔγϣϯʹࣦഊͨ͠ͱ͖͸ྫ֎ͱ͢Δ
    
22. "MXBZT
    WBMJE͸ຬ͍ͨͤͯΔ͕ʜʜ w ίϯετϥΫλͰ͸ࣄ্࣮ྫ֎ͰࣦഊΛ஌Βͤ Δ͔͠ͳ͍ͷͰɺऔΓճ͕͠ޮ͔ͳ͍ʢҰԠ TDBMBVUJM5SZͰͳΜͱ͔ग़དྷΔʣ
    w όϦσʔγϣϯΛॻ͔ͳ͍ϛε͸๷͛ͳ͍ʢς ετॻ͜͏Ͷʣ
    w ͳΜͱ͔͸ͳΔ͕ɺͳΜ͔ͩΜͩ৽ͨͳ໰୊͕ ු্ͯ͘͠Δ
23. 4DBMBͰ"MXBZT
    WBMJEΛ࣮ݱ͢Δվ class Person private (val name: String, val age: Int) object Person { def spawn(name: Indefinite[String], age: Indefinite[Int]): Person = { // ... } }
24. 4DBMBͰ"MXBZT
    WBMJEΛ࣮ݱ͢Δվ class Person private (val name: String, val age: Int) object Person { def spawn(name: Indefinite[String], age: Indefinite[Int]): Person = { // ... } } ίϯετϥΫλΛQSJWBUFʹ͢ΔʢΫϥεࣗମ͸QVCMJDʣ
    
25. 4DBMBͰ"MXBZT
    WBMJEΛ࣮ݱ͢Δվ class Person private (val name: String, val age: Int) object Person { def spawn(name: Indefinite[String], age: Indefinite[Int]): Person = { // ... } } TQBXOϝιουܦ༝ͰͷΈ1FSTPOΫϥεͷΠϯελϯεΛੜ੒Մೳ
    
26. 4DBMBͰ"MXBZT
    WBMJEΛ࣮ݱ͢Δվ class Person private (val name: String, val age: Int) object Person { def spawn(name: Indefinite[String], age: Indefinite[Int]): Person = { // ... } } ܕΛม͑ͯ௚઀౉ͤͳ͍Α͏ʹ͢Δ
    
27. class Indefinite[A](value: A) { def validateWith(validateValue: A => List[String]): Validity[A] = { val errors = validateValue(value) if (errors.isEmpty) Valid(value) else Invalid(errors) } } sealed trait Validity[+A] { def value: A def errors: List[String] } case class Valid[A](value: A) extends Validity[A] { val errors = List.empty } case class Invalid(errors: List[String]) extends Validity[Nothing] { def value = throw new NoSuchElementException("Invalid") } 4DBMBͰ"MXBZT
    WBMJEΛ࣮ݱ͢Δվ
28. class Indefinite[A](value: A) { def validateWith(validateValue: A => List[String]): Validity[A] = { val errors = validateValue(value) if (errors.isEmpty) Valid(value) else Invalid(errors) } } sealed trait Validity[+A] { def value: A def errors: List[String] } case class Valid[A](value: A) extends Validity[A] { val errors = List.empty } case class Invalid(errors: List[String]) extends Validity[Nothing] { def value = throw new NoSuchElementException("Invalid") } ೚ҙͷܕʢ"ʣͷ஋ΛऔΔɻWBMͰम০͍ͯ͠ͳ͍ͷͰɺ֎෦ʹެ։͞Εͳ͍
    4DBMBͰ"MXBZT
    WBMJEΛ࣮ݱ͢Δվ
29. class Indefinite[A](value: A) { def validateWith(validateValue: A => List[String]): Validity[A] = { val errors = validateValue(value) if (errors.isEmpty) Valid(value) else Invalid(errors) } } sealed trait Validity[+A] { def value: A def errors: List[String] } case class Valid[A](value: A) extends Validity[A] { val errors = List.empty } case class Invalid(errors: List[String]) extends Validity[Nothing] { def value = throw new NoSuchElementException("Invalid") } WBMJEBUF8JUIϝιουͰ಺แ͍ͯ͠Δ஋ͷ༗ޮແޮΛ͔֬ΊΔ
    4DBMBͰ"MXBZT
    WBMJEΛ࣮ݱ͢Δվ
30. 4DBMBͰ"MXBZT
    WBMJEΛ࣮ݱ͢Δվ class Person private (val name: String, val age: Int) object Person { def spawn(name: Indefinite[String], age: Indefinite[Int]): Person = { (name.validateWith(validateName), age.validateWith(validateAge)) match { case (Valid(validName), Valid(validAge)) => new Person(validName, validAge) case (validityName, validityAge) => throw new Exception((validityName.errors ++ validityAge.errors).mkString(", ")) } } private def validateName(name: String): List[String] = { if (name.isEmpty) List("name cannot be blank") else List.empty } private def validateAge(age: Int): List[String] = { if (age < 0) List("age must be zero or a positive number") else List.empty } }
31. 4DBMBͰ"MXBZT
    WBMJEΛ࣮ݱ͢Δվ class Person private (val name: String, val age: Int) object Person { def spawn(name: Indefinite[String], age: Indefinite[Int]): Person = { (name.validateWith(validateName), age.validateWith(validateAge)) match { case (Valid(validName), Valid(validAge)) => new Person(validName, validAge) case (validityName, validityAge) => throw new Exception((validityName.errors ++ validityAge.errors).mkString(", ")) } } private def validateName(name: String): List[String] = { if (name.isEmpty) List("name cannot be blank") else List.empty } private def validateAge(age: Int): List[String] = { if (age < 0) List("age must be zero or a positive number") else List.empty } } WBMJEBUF8JUIʹόϦσʔγϣϯ༻ͷؔ਺Λ
    ౉͠ɺ಺แ͞Ε͍ͯΔ஋ͷ༗ޮແޮΛಘΔ
    
32. 4DBMBͰ"MXBZT
    WBMJEΛ࣮ݱ͢Δվ class Person private (val name: String, val age: Int) object Person { def spawn(name: Indefinite[String], age: Indefinite[Int]): Person = { (name.validateWith(validateName), age.validateWith(validateAge)) match { case (Valid(validName), Valid(validAge)) => new Person(validName, validAge) case (validityName, validityAge) => throw new Exception((validityName.errors ++ validityAge.errors).mkString(", ")) } } private def validateName(name: String): List[String] = { if (name.isEmpty) List("name cannot be blank") else List.empty } private def validateAge(age: Int): List[String] = { if (age < 0) List("age must be zero or a positive number") else List.empty } } ύλʔϯϚονͰ͢΂ͯ༗ޮͷͱ͖ͷΈ1FSTPOΫϥεͷΠϯελϯεΛੜ੒͢Δ
    
33. ࢖༻ྫ try { val name = new Indefinite("takkkun") val age = new Indefinite(-1) val person = Person.spawn(name, age) // handle person } catch { case e: Exception => // handle exception }
34. &JUIFSόʔδϣϯ object Person { def spawn(name: Indefinite[String], age: Indefinite[Int]): Either[List[String], Person] = { (name.validateWith(validateName), age.validateWith(validateAge)) match { case (Valid(validName), Valid(validAge)) => Right(new Person(validName, validAge)) case (validityName, validityAge) => Left(validityName.errors ++ validityAge.errors) } } // ... }
35. &JUIFSόʔδϣϯ࢖༻ྫ val name = new Indefinite("takkkun") val age = new Indefinite(-1) val errorsOrPerson = Person.spawn(name, age) errorsOrPerson match { case Left(errors) => // handle errors case Right(person) => // handle person }
36. ·ͱΊ w ʮΦϒδΣΫτ͕༗ޮ͔ແޮ͔ͱ͍͏ঢ়ଶʯΛ ࣋ͭͷ͸໘౗͞૿େͷஹީ
    w ނʹΦϒδΣΫτ͸ৗʹ༗ޮʢ"MXBZT
    WBMJEʣͰ ͋Εɺͱ͍͏ߟ͑ํ
    w 4DBMBͳͲͷ੩తܕ෇͚ݴޠͰ͋Ε͹ɺܕͰόϦ σʔγϣϯʹڧ੍ྗΛ࣋ͨͤΒΕΔ
37. ϦϥΫͰ͸։ൃऀΛืू͍ͯ͠·͢ w ීஈ͜͏͍͏͜ͱΛߟ͑ͳ͕Β։ൃ͍ͯ͠·͢
    w αʔόʔαΠυ͸4DBMB͕ओ
    w J04
    4XJGU
    "OESPJE΋
    w ΍Δ͜ͱ͍ͬͺ͍͋Δ
    w ڵຯ͕͋Δํ͸
    !UBLLLVO
    ·Ͱ
38. ͓͠·͍