Rork Max のアプリで iOS 18 のオンデバイス翻訳を使う — 無料・オフラインで多言語ユーザーに応える

import SwiftUI
import Translation
 
struct ReviewTranslateView: View {
    let originalText: String                 // 海外ユーザーが書いた原文
    @State private var translated = ""
    @State private var configuration: TranslationSession.Configuration?
 
    var body: some View {
        VStack(alignment: .leading, spacing: 12) {
            Text(originalText)
 
            if !translated.isEmpty {
                Text(translated)
                    .foregroundStyle(.secondary)
            }
 
            Button("日本語に訳す") {
                if configuration == nil {
                    // source を nil にすると、入力文の言語を自動判定します
                    configuration = .init(
                        source: nil,
                        target: Locale.Language(identifier: "ja")
                    )
                } else {
                    // 同じ構成のまま押し直したときに再実行させる
                    configuration?.invalidate()
                }
            }
        }
        .translationTask(configuration) { session in
            do {
                let response = try await session.translate(originalText)
                translated = response.targetText      // 訳文はここに入る
            } catch {
                translated = "翻訳に失敗しました（\(error.localizedDescription)）"
            }
        }
    }
}

import Translation
 
enum TranslateReadiness {
    case ready            // すぐ翻訳できる
    case needsDownload    // 対応しているが、モデルが未DL
    case unsupported      // この言語ペアは非対応
}
 
func checkReadiness(from source: Locale.Language) async -> TranslateReadiness {
    let availability = LanguageAvailability()
    let target = Locale.Language(identifier: "ja")
    let status = await availability.status(from: source, to: target)
 
    switch status {
    case .installed:   return .ready
    case .supported:   return .needsDownload
    case .unsupported: return .unsupported
    @unknown default:  return .unsupported
    }
}

.translationTask(configuration) { session in
    do {
        // 未DLならここでシステムのダウンロード確認が出る。DL済みなら即返る
        try await session.prepareTranslation()
        let response = try await session.translate(originalText)
        translated = response.targetText
    } catch {
        translated = "翻訳を準備できませんでした（\(error.localizedDescription)）"
    }
}

struct UserComment: Identifiable {
    let id: Int
    let body: String
    var translated: String = ""
}
 
func translateAll(_ comments: inout [UserComment],
                  session: TranslationSession) async throws {
    // 各リクエストに clientIdentifier を付け、応答と突き合わせる
    let requests = comments.map { comment in
        TranslationSession.Request(
            sourceText: comment.body,
            clientIdentifier: "\(comment.id)"
        )
    }
 
    let responses = try await session.translations(from: requests)
 
    // 応答は順不同で届くことがあるため、識別子でインデックスを引く
    let indexByID = Dictionary(
        uniqueKeysWithValues: comments.enumerated().map { ($0.element.id, $0.offset) }
    )
    for response in responses {
        if let id = response.clientIdentifier.flatMap(Int.init),
           let i = indexByID[id] {
            comments[i].translated = response.targetText
        }
    }
}