RailsのValidatesをSwift Macrosで再現してみた

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   ͷόϦσʔγϣϯ class Article < ApplicationRecord validates :title, :body, presence: true validates :status, inclusion: { in: %w[draft published] } validates :title, length: { maximum: 100 } validates :email, format: { with: URI::MailTo::EMAIL_REGEXP } end > article.valid? #=> true or false
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   .BDSPTͰ࠶ݱ @Validatable struct Article { var title: String var body: String var status: Status var email: String? #Validation(\Self.title, \.body, presence: .required) #Validation(\Self.status, inclusion: [.draft, .published]) #Validation(\Self.title, countWithin: ...100) #Validation(\Self.email, format: /^[a-zA-Z0-9._%+-]+@.+\..{2,}$/) } > article.isValid > try article.validate() IUUQTHJUIVCDPNIPLVSPOTXJGUWBMJEBUJPOT IPLVSPOTXJGUWBMJEBUJPOT
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   validates :age, length: { minimum: 16 } // ⚠ ܻ਺νΣοΫͱͳΓҙਤ͠ͳ͍ݕূ݁ՌʹͳΔɻ͜ͷ৔߹numericalityݕূΛ͢Δͷ ͕ਖ਼͍͠ɻ 4XJGU
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   #Validation(\Self.age, countWithin: 16…) // ❌ Macro 'Validation(_:countWithin:where:)' requires that 'Int' conform to 'Collection'
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7. .BDSPͷ࣮૷ w #Validation
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   struct ValidationMacro: DeclarationMacro { public static func expansion(...) throws -> [DeclSyntax] { return [] // ۭ഑ྻΛฦ͠ίʔυੜ੒΋ͳ͍ } } w @Validatable
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8. @Validatable struct User { var name: String var age: UInt var email: String? var bio: String? var password: String #Validation(\Self.name, presence: .required) #Validation(\Self.age, comparison: .greaterThan(16)) #Validation(\Self.email, format: /…/, presence: .required(allowsNil: true)) #Validation(\Self.bio, presence: .none) #Validation(\Self.password, presence: .required(allowsEmpty: true)) }
9. @Validatable struct User { var name: String var age: UInt var email: String? var bio: String? var password: String #Validation(\Self.name, presence: .required) #Validation(\Self.age, comparison: .greaterThan(16)) #Validation(\Self.email, format: /…/, presence: .required(allowsNil: true)) #Validation(\Self.bio, presence: .none) #Validation(\Self.password, presence: .required(allowsEmpty: true)) } ˣੜ੒ίʔυ
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   extension User: Validations.Validatable { var validation: some Validator { Presence(of: self[keyPath: \Self.name]).presence(.required) .errorKey(Self.self, \Self.name) Comparison(of: self[keyPath: \Self.age], .greaterThan(16)) .errorKey(Self.self, \Self.age) Format(of: self[keyPath: \Self.email], with: /…/).presence(.required(allowsNil: true)) .errorKey(Self.self, \Self.email) Presence(of: self[keyPath: \Self.bio]).presence(.none) .errorKey(Self.self, \Self.bio) Presence(of: self[keyPath: \Self.password]).presence(.required(allowsEmpty: true)) .errorKey(Self.self, \Self.password) } }
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