Swift4.2で追加されたDynamic Member Lookupを使ってみよう

try! Swift Pre Talks でお話ししました登壇資料です @tamappe

Transcript

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2. struct Me {
   let name = “Yosuke Tamaoki”
   let age = 31
   let company = “Summer" + “Freelance“
   let os = "iOS" + "Android"
   let hobby = "Splatoon2" + “Poker"
   struct Language {
   let swift
   let objective-c
   let java
   let kotlin
   }
   }
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4. // Dictionary
   let classRoom: [String: Any] = [
   "teacher": "Yamada",
   “studentNum”: 30
   ]
   // before
   let teacher = classRoom["teacher"] // "Yamada"
   let count = classRoom["studentNum"] // 30
   let teacher = classRoom.teacher // compile error
   let count = classRoom.studentNum // compile error
   // after
   let teacher = classRoom.teacher // "Yamada"
   let count = classRoom.studentNum // 30
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7. $MBTTDBTF
   @dynamicMemberLookup
   class User {
   let firstName: String
   let lastName: String
   let age: Int
   init(firstName: String, lastName: String, age: Int) {
   self.firstName = firstName
   self.lastName = lastName
   self.age = age
   }
   subscript(dynamicMember key: String) -> Any {
   switch key {
   case "upperFirstName":
   return firstName.uppercased()
   case "upperLastName":
   return lastName.uppercased()
   case "adalt":
   return 30
   case "children":
   return 15
   default:
   return ""
   }
   }
   }
   

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8. $MBTTDBTF
   @dynamicMemberLookup
   class User {
   let firstName: String
   let lastName: String
   let age: Int
   init(firstName: String, lastName: String, age: Int) {
   self.firstName = firstName
   self.lastName = lastName
   self.age = age
   }
   subscript(dynamicMember key: String) -> Any {
   switch key {
   case "upperFirstName":
   return firstName.uppercased()
   case "upperLastName":
   return lastName.uppercased()
   case "adalt":
   return 30
   case "children":
   return 15
   default:
   return ""
   }
   }
   }
   

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9. 6TFDBTF
   let hanakoYamada = User(firstName: "Hanako",
   lastName: "Yamada",
   age: 20)
   print(hanakoYamada.firstName) // "Hanako"
   print(hanakoYamada.lastName) // "Yamada"
   print(hanakoYamada.age) // 20
   print(hanakoYamada.upperFirstName) // "HANAKO"
   print(hanakoYamada.upperLastName) // "YAMADA"
   print(hanakoYamada.adalt) // 30
   print(hanakoYamada.children) // 15
   print(hanakoYamada.young) // ""
   

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10. TUSVDUDBTF
    @dynamicMemberLookup
    struct Person {
    subscript(dynamicMember name: String) -> String {
    return "Hello, \(name)"
    }
    }
    

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11. TUSVDUDBTF
    @dynamicMemberLookup
    struct Person {
    subscript(dynamicMember name: String) -> String {
    return "Hello, \(name)"
    }
    }
    

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12. 6TFDBTF
    let person = Person()
    print(person.swift) // "Hello, swift”
    print(person.hanako) // "Hello, hanako”
    print(person.taro) // "Hello, taro"
    

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13. 5IBU`T"MM
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    https://blog.tamappe.com
    

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14. 1SPUPDPMDBTF
    @dynamicMemberLookup
    protocol SampleProtocol {
    associatedtype Key
    associatedtype Value
    subscript(key: Key) -> Value? { get }
    }
    extension SampleProtocol where Key == String {
    subscript(dynamicMember member: String) -> Value? {
    return self[member]
    }
    }
    extension Dictionary: SampleProtocol {}
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15. 6TFDBTF
    let hanakoDic: [String : Any] = [
    "firstName": "hanako",
    "lastName": "yamada",
    "age": 20
    ]
    print(hanakoDic.firstName as! String) // “hanako"
    print(hanakoDic.age as! Int) // 20
    

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16. &OVNDBTF
    @dynamicMemberLookup
    enum JSON {
    case number(Int)
    case string(String)
    case array([JSON])
    case dictionary([String: JSON])
    subscript(dynamicMember key: String) -> JSON? {
    guard case .dictionary(let dict) = self else {
    return nil
    }
    return dict[key]
    }
    }
    extension JSON {
    var numberValue: Int? {
    guard case .number(let n) = self else {
    return nil
    }
    return n
    }
    var stringValue: String? {
    guard case .string(let s) = self else {
    return nil
    }
    return s
    }
    subscript(index: Int) -> JSON? {
    guard case .array(let arr) = self,
    arr.indices.contains(index) else
    {
    return nil
    }
    return arr[index]
    }
    subscript(key: String) -> JSON? {
    guard case .dictionary(let dict) = self else {
    return nil
    }
    return dict[key]
    }
    }
    +40/
    

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17. &OVNDBTF
    @dynamicMemberLookup
    enum JSON {
    case number(Int)
    case string(String)
    case array([JSON])
    case dictionary([String: JSON])
    subscript(dynamicMember key: String) -> JSON? {
    guard case .dictionary(let dict) = self else {
    return nil
    }
    return dict[key]
    }
    }
    +40/
    

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18. &OVNDBTF
    extension JSON {
    var numberValue: Int? {
    guard case .number(let n) = self else {
    return nil
    }
    return n
    }
    var stringValue: String? {
    guard case .string(let s) = self else {
    return nil
    }
    return s
    }
    subscript(index: Int) -> JSON? {
    guard case .array(let arr) = self,
    arr.indices.contains(index) else
    {
    return nil
    }
    return arr[index]
    }
    subscript(key: String) -> JSON? {
    guard case .dictionary(let dict) = self else {
    return nil
    }
    return dict[key]
    }
    }
    +40/
    

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19. 6TFDBTF
    let json = JSON.dictionary([
    "firstName": .string("hanako"),
    "lastName": .string("Yamada"),
    "age": .number(20),
    "language": .array([
    .string(“Swift"),
    .string("Objective-c"),
    .string("Kotlin"),
    .string("Java"),
    ])
    ])
    if let firstName = json.firstName?.stringValue {
    print(firstName) // "hanako"
    }
    

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