[Swift - UIKit] BaseView, APIService 싱글턴 패턴, DispatchGroup 등을 활용한 간단한 영화 평점 매기기 서비스를 구현해보았다.

class BaseView: UIView {
    @available(*, unavailable)
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override init(frame: CGRect) {
        super.init(frame: frame)

        configureSubView()
        configureLayout()
        configureUI()
    }

    func configureSubView() {}
    func configureLayout() {}
    func configureUI() {}
}

class SomeViewController: BaseViewController {
    private let mainView = SomeMainView()

    override func loadView() {
        self.view = mainView
    } 

    override func viewDidLoad() {
        super.viewDidLoad()
        mainView.label.xxx // 변경된 뷰 객체의 속성들에 접근하는 형식으로 코드를 작성한다.
    }
}

class APIService {
    private init() {}
    
    static let manager = APIService()
    
    private let base = BASE
    private let headers = HEADERS
    
    enum ServiceType {
        case current
        case trend
        case search(query: String)
        case detail(id: Int)
    }
    
    private func serviceEndPoint(_ type: ServiceType) -> String {
        switch type {
        case .current:
            return "movie/now_playing"
        case .trend:
            return "trending/movie/day"
        case .search(let query):
            return "search/movie?query=\(query)"
        case .detail(let id):
            return "movie/\(String(id))"
        }
    }
    
    private func serviceMethod(_ type: ServiceType) -> HTTPMethod {
        switch type {
        case .current, .trend, .search, .detail:
            return .get
        }
    }
    
    private func genRequest(_ type: ServiceType) -> DataRequest {
        return AF.request(
            self.base + self.serviceEndPoint(type),
            method: self.serviceMethod(type),
            parameters: ["language": "ko-KR"],
            encoding: URLEncoding(destination: .queryString),
            headers: self.headers
        )
    }
    
    typealias SuccessHandler<T: Decodable> = (T) -> ()
    typealias ErrorHandler = (any Error) -> ()
    
    func fetch<T: Decodable>(
      _ serviceType: ServiceType, 
      successHandler: @escaping SuccessHandler<T>, 
      errorHandler: @escaping ErrorHandler) {
        
        self.genRequest(serviceType).responseDecodable(of: T.self) { response in
            do {
                let data = try response.result.get()
                successHandler(data)
            } catch {
                errorHandler(error)
            }
        }
      
    }
}

override func viewDidLoad() {
    super.viewDidLoad()
    fetchData()
}

func fetchData() {
    let group = DispatchGroup()
  
    [.current, .trend, .topRated].enumerated().forEach { (index, type) in
            group.enter()
            DispatchQueue.global().async(group: group) {
                APIService.manager.fetch(type) { (data: Movie) in
                    self.listDatas[index] = data.results
                    group.leave()
                } errorHandler: { error in
                    group.leave()
                }

            }
        }
        
    group.notify(queue: .main) {
        self.mainView.table.reloadSections(IndexSet(integer: 0), with: .none)
    }
}