Usage of Async/Await in UIKit based iOS Application

async-await dataTask

// Referenaces
// https://developer.apple.com/videos/play/wwdc2021/10095/
// https://swiftly.dev/async-await
// https://www.avanderlee.com/swift/async-await/
// https://swiftsenpai.com/swift/async-await-network-requests/

enum CustomError: Error {
    case invalidRequest
    case unsupportedImage
}

final class Downloader {
    static let shared: Downloader = Downloader()
    private var dataTasks: Set<URLSessionDataTask> = Set<URLSessionDataTask>()
    private let session = URLSession.shared
    private var imageCache = NSCache<NSURL, UIImage>()

    func downloadImg(url: URL) async throws -> UIImage  {
        let (data, response) = try await session.data(from: url)
        guard let httpResponse = response as? HTTPURLResponse,
              httpResponse.statusCode == 200
        else {
            throw CustomError.invalidRequest
        }
        
        guard let image = UIImage(data: data) else {
            throw CustomError.unsupportedImage
        }
        return image
    }
}

class ViewModel {
  func downloadImg() async -> UIImage? {
        guard let urlString = currentQuestion.questionImageUrl,
              isValidUrl(url: urlString),
              let url = URL(string: urlString)
        else {
            return nil
        }
        
        do {
            return try await imageDownloader.downloadImg(url: url)
        } catch {
            return nil
        }
    }
}

class ViewController {
  var image: UIImage?
  
  func fetchAndShowImage() {
    Task {
      image = viewModel.downloadImg()
    }
  }
}