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

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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 } } "CPVU
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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 1PXFS
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7. $MBTT
   DBTF @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 "" } } }
8. $MBTT
   DBTF @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 "" } } }
9. 6TF
   DBTF 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) // ""
10. TUSVDU
    DBTF
    @dynamicMemberLookup struct Person { subscript(dynamicMember name: String) -> String { return "Hello, \(name)" } }
11. TUSVDU
    DBTF
    @dynamicMemberLookup struct Person { subscript(dynamicMember name: String) -> String { return "Hello, \(name)" } }
12. 6TF
    DBTF let person = Person() print(person.swift) // "Hello, swift” print(person.hanako) // "Hello, hanako” print(person.taro) // "Hello, taro"
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14. 1SPUPDPM
    DBTF
    @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 {} 1SPUPDPM
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15. 6TF
    DBTF let hanakoDic: [String : Any] = [ "firstName": "hanako", "lastName": "yamada", "age": 20 ] print(hanakoDic.firstName as! String) // “hanako" print(hanakoDic.age as! Int) // 20
16. &OVN
    DBTF
    @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/
17. &OVN
    DBTF
    @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/
18. &OVN
    DBTF
    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/
19. 6TF
    DBTF 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" }