PropertyWrapperを利用したDependendyInjectionの例（各ドメイン側）

DependenciesForDomains.swift

// (1) APIRequestManager.swift
// Infra層部分

import Foundation
import RxSwift

// MARK: - Protocol

protocol APIRequestProtocol {
    func getAnnoucements() -> Single<AnnouncementListResponse>
}

// MARK: - APIRequestManagerProtocol

extension APIRequestManager: APIRequestProtocol {

    // お知らせ一覧表示用のAPIリクエスト処理の実行
    func getAnnoucements() -> Single<AnnouncementListResponse> {

        let annoucementListsEndPoint = EndPoint.announcement.getBaseUrl()
        return executeAPIRequest(
            endpointUrl: annoucementListsEndPoint,
            httpMethod: HTTPMethod.GET,
            responseFormat: AnnouncementListResponse.self
        )
    }
}

// (2) AnnoucementRepositoryImpl.swift
// Domain層部分
import Foundation
import RxSwift

// MARK: - Protocol

protocol AnnoucementRepository {

    // お知らせ一覧表示用のAPIリクエストを実行する
    func requestAnnouncementDataList() -> Single<AnnouncementListResponse>
}

final class AnnoucementRepositoryImpl: AnnoucementRepository {

    // MARK: - Properties

    @Dependencies.Inject(Dependencies.Name(rawValue: "APIRequestProtocol")) private var apiRequestManager: APIRequestProtocol

    // MARK: - AnnoucementRepository

    func requestAnnouncementDataList() -> Single<AnnouncementListResponse> {
        return apiRequestManager.getAnnoucements()
    }
}

// (3) AnnouncementUseCaseImpl.swift
// UseCase層部分

import Foundation
import RxSwift

// MARK: - Protocol

protocol AnnouncementUsecase {

    // お知らせ一覧取得処理を実行する
    func execute() -> Single<AnnouncementListResponse>
}

final class AnnouncementUseCaseImpl: AnnouncementUsecase {

    // MARK: - Properties

    @Dependencies.Inject(Dependencies.Name(rawValue: "AnnoucementRepository")) private var annoucementRepository: AnnoucementRepository

    // MARK: - AnnouncementUsecase

    func execute() -> Single<AnnouncementListResponse> {
        return annoucementRepository.requestAnnouncementDataList()
    }
}

// (4) AnnouncementViewModel.swift
// ViewModel層部分

import Foundation
import RxSwift
import RxCocoa

protocol AnnouncementViewModelInputs {

    // 初回のデータ取得をViewModelへ伝える
    var initialFetchTrigger: PublishSubject<Void> { get }

    // PullToRefreshでのデータ更新をViewModelへ伝える
    var pullToRefreshTrigger: PublishSubject<Void> { get }
}

protocol AnnouncementViewModelOutputs {

    // JSONから取得した表示用データを格納する
    var announcementItems: Observable<Array<AnnouncementEntity>> { get }

    // 取得処理の実行結果を格納する
    var requestStatus: Observable<APIRequestState> { get }
}

protocol AnnouncementViewModelType {
    var inputs: AnnouncementViewModelInputs  { get }
    var outputs: AnnouncementViewModelOutputs { get }
}

final class AnnouncementViewModel: AnnouncementViewModelInputs, AnnouncementViewModelOutputs, AnnouncementViewModelType {

    var inputs: AnnouncementViewModelInputs { return self }
    var outputs: AnnouncementViewModelOutputs { return self }

    // MARK: - Properties (for AnnouncementViewModelInputs)

    let initialFetchTrigger: PublishSubject<Void> = PublishSubject<Void>()

    let pullToRefreshTrigger: PublishSubject<Void> = PublishSubject<Void>()

    // MARK: - Properties (for AnnouncementViewModelOutputs)

    var announcementItems: Observable<Array<AnnouncementEntity>> {
        return _announcementItems.asObservable()
    }

    var requestStatus: Observable<APIRequestState> {
        return _requestStatus.asObservable()
    }

    // MARK: - Properties

    private let disposeBag = DisposeBag()

    // MEMO: 中継地点となるBehaviorRelayの変数（Outputの変数を生成するための「つなぎ」のような役割）
    // → BehaviorRelayの変化が起こったらObservableに変換されてOutputに流れてくる
    private let _announcementItems: BehaviorRelay<Array<AnnouncementEntity>> = BehaviorRelay<Array<AnnouncementEntity>>(value: [])
    private let _requestStatus: BehaviorRelay<APIRequestState> = BehaviorRelay<APIRequestState>(value: .none)

    // MEMO: このViewModelで利用するUseCase(Domain Model)
    @Dependencies.Inject(Dependencies.Name(rawValue: "AnnouncementUsecase")) private var announcementUsecase: AnnouncementUsecase

    // MARK: - Initializer

    init() {

        // ViewModel側の処理実行トリガーと連結させる
        initialFetchTrigger
            .subscribe(
                onNext: { [weak self] _ in
                    guard let self = self else { return }
                    self.executeAnnouncementDataRequest()
                }
            )
            .disposed(by: disposeBag)
        pullToRefreshTrigger
            .subscribe(
                onNext: { [weak self] _ in
                    guard let self = self else { return }
                    self.executeAnnouncementDataRequest()
                }
            )
            .disposed(by: disposeBag)
    }

    // MARK: - Private Function

    private func executeAnnouncementDataRequest() {
        _requestStatus.accept(.requesting)
        announcementUsecase.execute()
            .subscribe(
                onSuccess: { [weak self] data in
                    guard let self = self else { return }
                    self._requestStatus.accept(.success)
                    self._announcementItems.accept(data.result)
                },
                onError: { [weak self] error in
                    guard let self = self else { return }
                    self._requestStatus.accept(.error)
                }
            )
            .disposed(by: disposeBag)
    }
}

// (5) AnnouncementViewController.swift
// ViewController層部分

final class AnnouncementViewController: UIViewController {

    // ... （※Dependency Injection部分のみ抜粋） ...

    // MEMO: お知らせ表示状態をハンドリングするViewModel
    @Dependencies.Inject(Dependencies.Name(rawValue: "AnnouncementViewModelType")) private var viewModel: AnnouncementViewModelType

    // ... 以下省略 ...
}