Fix crash when subscribe for activities is too early #4420

AlphaWallet/Activities/Coordinators/ActivitiesCoordinator.swift

@@ -10,7 +10,7 @@ protocol ActivitiesCoordinatorDelegate: AnyObject {
 class ActivitiesCoordinator: NSObject, Coordinator {
     private let sessions: ServerDictionary<WalletSession>
     private let activitiesService: ActivitiesServiceType
-    private var subscriptionKey: Subscribable<ActivitiesViewModel>.SubscribableKey!
+    private var subscriptionKey: Subscribable<ActivitiesViewModel>.SubscribableKey?
     private let keystore: Keystore
     private let wallet: Wallet
     private let analyticsCoordinator: AnalyticsCoordinator
@@ -38,16 +38,11 @@ class ActivitiesCoordinator: NSObject, Coordinator {
         self.keystore = keystore
         self.wallet = wallet
         super.init()
-
-        subscriptionKey = activitiesService.subscribableViewModel.subscribe { [weak self] viewModel in
-            guard let strongSelf = self, let viewModel = viewModel else { return }
-
-            strongSelf.rootViewController.configure(viewModel: viewModel)
-        }
     }
 
     func start() {
         navigationController.viewControllers = [rootViewController]
+        subscribeForActivitiesUpdates()
     }
 
     private func makeActivitiesViewController() -> ActivitiesViewController {
@@ -68,6 +63,17 @@ class ActivitiesCoordinator: NSObject, Coordinator {
 }
 
 extension ActivitiesCoordinator: ActivitiesViewControllerDelegate {
+
+    func subscribeForActivitiesUpdates() {
+        subscriptionKey.flatMap { activitiesService.subscribableViewModel.unsubscribe($0) }
+
+        subscriptionKey = activitiesService.subscribableViewModel.subscribe { [weak rootViewController] viewModel in
+            guard let viewController = rootViewController, let viewModel = viewModel else { return }
+
+            viewController.configure(viewModel: viewModel)
+        }
+    }
+
     func didPressActivity(activity: Activity, in viewController: ActivitiesViewController) {
         delegate?.didPressActivity(activity: activity, in: viewController)
     }

AlphaWallet/Activities/ViewControllers/ActivitiesViewController.swift

@@ -13,7 +13,9 @@ class ActivitiesViewController: UIViewController {
     private var viewModel: ActivitiesViewModel
     private let searchController: UISearchController
     private var isSearchBarConfigured = false
-    private var bottomConstraint: NSLayoutConstraint!
+    private lazy var bottomConstraint: NSLayoutConstraint = {
+        return activitiesView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
+    }()
     private lazy var keyboardChecker = KeyboardChecker(self, resetHeightDefaultValue: 0, ignoreBottomSafeArea: true)
     private var activitiesView: ActivitiesView
     weak var delegate: ActivitiesViewControllerDelegate?
@@ -24,11 +26,7 @@ class ActivitiesViewController: UIViewController {
         activitiesView = ActivitiesView(analyticsCoordinator: analyticsCoordinator, keystore: keystore, wallet: wallet, viewModel: viewModel, sessions: sessions)
         super.init(nibName: nil, bundle: nil)
 
-        title = R.string.localizable.activityTabbarItemTitle()
         activitiesView.delegate = self
-        view.backgroundColor = viewModel.backgroundColor
-
-        bottomConstraint = activitiesView.bottomAnchor.constraint(equalTo: view.bottomAnchor)
         keyboardChecker.constraints = [bottomConstraint]
 
         view.addSubview(activitiesView)
@@ -41,6 +39,11 @@ class ActivitiesViewController: UIViewController {
         ])
 
         setupFilteringWithKeyword()
+    }
+
+    override func viewDidLoad() {
+        super.viewDidLoad()
+
         configure(viewModel: viewModel)
     }
 
@@ -70,6 +73,8 @@ class ActivitiesViewController: UIViewController {
     func configure(viewModel: ActivitiesViewModel) {
         self.viewModel = viewModel
 
+        title = R.string.localizable.activityTabbarItemTitle()
+        view.backgroundColor = viewModel.backgroundColor
         activitiesView.configure(viewModel: viewModel)
         activitiesView.applySearch(keyword: searchController.searchBar.text)