StoryKitManager is a helper for subscription purchase

AppDelegate.swift

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
  let storeManager = StoreKitManager()
  var window: UIWindow?

  func application(_ application: UIApplication,
                   didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    storeManager.setup()
    return true
  }
}

StoryKitManager.swift

import StoreKit
import SwiftyStoreKit

class StoreKitManager {

  // MARK: Properties
  var sharedSecret: String {
    return ""
  }

  var appBundleId: String {
    return Bundle.main.bundleIdentifier ?? ""
  }

  // MARK: Enums
  enum RegisteredPurchase: String {
    case weeklysubscription
    case yearlysubscription
  }

  // MARK: Public Methods
  func setup() {
    SwiftyStoreKit.completeTransactions { purchases in
      for purchase in purchases {
        switch purchase.transaction.transactionState {
        case .purchased, .restored:
          let downloads = purchase.transaction.downloads
          if !downloads.isEmpty {
            SwiftyStoreKit.start(downloads)
          } else if purchase.needsFinishTransaction {
            SwiftyStoreKit.finishTransaction(purchase.transaction)
          }
          print("💵 Transaction State ➭ \(purchase.transaction.transactionState.debugDescription): \(purchase.productId)")
        default:
          break
        }
      }
    }

    SwiftyStoreKit.updatedDownloadsHandler = { downloads in
      let contentURLs = downloads.compactMap { $0.contentURL }
      if contentURLs.count == downloads.count {
        print("💵 Content URLs ➭ \(contentURLs)")
        SwiftyStoreKit.finishTransaction(downloads[0].transaction)
      }
    }
  }

  func getInfo(_ purchase: RegisteredPurchase, completion: @escaping (RetrieveResults?) -> Void) {
    SwiftyStoreKit.retrieveProductsInfo([appBundleId + "." + purchase.rawValue]) { result in
      completion(result)
    }
  }

  func purchase(_ purchase: RegisteredPurchase,
                atomically: Bool = true,
                completion: @escaping (PurchaseDetails?, SKError?) -> Void) {
    SwiftyStoreKit.purchaseProduct(appBundleId + "." + purchase.rawValue, atomically: atomically) { result in
      switch result {
      case .success(let purchase):
        let downloads = purchase.transaction.downloads
        if !downloads.isEmpty {
          SwiftyStoreKit.start(downloads)
        }
        if purchase.needsFinishTransaction {
          SwiftyStoreKit.finishTransaction(purchase.transaction)
        }
        completion(purchase, nil)
      case .error(let error):
        completion(nil, error)
      }
    }
  }

  func verifyPurchase(_ purchase: RegisteredPurchase,
                      completion: @escaping (VerifySubscriptionResult?, ReceiptError?) -> Void) {
    verifyReceipt { result in
      switch result {
      case .success(let receipt):
        let productId = self.appBundleId + "." + purchase.rawValue
        switch purchase {
        case .weeklysubscription, .yearlysubscription:
          let purchaseResult = SwiftyStoreKit.verifySubscription(
            ofType: .autoRenewable,
            productId: productId,
            inReceipt: receipt
          )
          completion(purchaseResult, nil)
        }
      case .error(let error):
        completion(nil, error)
      }
    }
  }

  func restorePurchases(completion: @escaping (RestoreResults) -> Void) {
    SwiftyStoreKit.restorePurchases(atomically: true) { results in
      for purchase in results.restoredPurchases {
        let downloads = purchase.transaction.downloads
        if !downloads.isEmpty {
          SwiftyStoreKit.start(downloads)
        } else if purchase.needsFinishTransaction {
          SwiftyStoreKit.finishTransaction(purchase.transaction)
        }
      }
      completion(results)
    }
  }

  private func verifyReceipt(completion: @escaping (VerifyReceiptResult) -> Void) {
    let appleValidator = AppleReceiptValidator(service: .production, sharedSecret: sharedSecret)
    SwiftyStoreKit.verifyReceipt(using: appleValidator, completion: completion)
  }
}

ViewController.swift

import UIKit

class ViewController: UIViewController {

  private let storeManager = StoreKitManager()

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

  @IBAction private func yearlySubscibe() {
    storeManager.purchase(.yearlysubscription) { details, error in
      print("💵 Purchase Success ➭ \(String(describing: details))")
    }
  }

  @IBAction private func weeklySubscibe() {
    storeManager.purchase(.weeklysubscription) { details, error in
      print("💵 Purchase Success ➭ \(String(describing: details))")
    }
  }

  @IBAction private func restore() {
    storeManager.restorePurchases { results in
      print("💵 Restore Purchases ➭ \(results)")
    }
  }

  private func validate() {
    storeManager.getInfo(.weeklysubscription) { result in
      print("💵 Retrieve Results Weekly ➭ \(String(describing: result?.retrievedProducts.first?.localizedTitle))")
    }

    storeManager.getInfo(.yearlysubscription) { result in
      print("💵 Retrieve Results yearly ➭ \(String(describing: result?.retrievedProducts.first?.localizedTitle))")
    }

    storeManager.verifyPurchase(.weeklysubscription) { result, error in
      guard let error = error else { return }
      print("❌ Weekly Error: \(error.localizedDescription)")
      self.storeManager.verifyPurchase(.yearlysubscription) { result, error in
        guard let error = error else { return }
        print("❌ Yearly Error: \(error.localizedDescription)")
      }
    }
  }
}