Forecast: fix (hopefully) infinite recursion in `scrollViewDidScroll`.

1Weather/UI/View controllers/Forecast/ForecastViewController.swift

@@ -23,6 +23,8 @@ class ForecastViewController: UIViewController {
         return TimePeriod(rawValue: timePeriodControl.selectedSegmentIndex) ?? .daily
     }
     
+    private var navigationBarStateBeingChanged = false
+    
     init(viewModel: ForecastViewModel, coordinator: ForecastCoordinator) {
         self.viewModel = viewModel
         self.coordinator = coordinator
@@ -188,6 +190,7 @@ private extension ForecastViewController {
 extension ForecastViewController: UITableViewDelegate {
     func scrollViewDidScroll(_ scrollView: UIScrollView) {
         guard
+            !navigationBarStateBeingChanged,
             let navVC = self.navigationController,
             viewModel.location?.daily.isEmpty == false,
             self.timePeriod == .daily
@@ -200,18 +203,27 @@ extension ForecastViewController: UITableViewDelegate {
         }
 
         let startPointY = timePeriodCellFrame.origin.y + timePeriodCellFrame.height - self.daysControlView.frame.height
+        let animationDuration = TimeInterval(UINavigationController.hideShowBarDuration)
         
         if scrollView.contentOffset.y >= startPointY {
             if !navVC.isNavigationBarHidden {
+                self.navigationBarStateBeingChanged = true
+                DispatchQueue.main.asyncAfter(deadline: .now() + animationDuration) {
+                    self.navigationBarStateBeingChanged = false
+                }
                 navVC.setNavigationBarHidden(true, animated: true)
                 self.daysControlView.update(offset: self.viewModel.offsetHolder.currentOffset)
-                UIView.animate(withDuration: 0.35) {
+                UIView.animate(withDuration: animationDuration) {
                     self.daysControlView.alpha = 1
                 }
             }
         }
         else {
             if navVC.isNavigationBarHidden {
+                self.navigationBarStateBeingChanged = true
+                DispatchQueue.main.asyncAfter(deadline: .now() + animationDuration) {
+                    self.navigationBarStateBeingChanged = false
+                }
                 navVC.setNavigationBarHidden(false, animated: true)
                 UIView.animate(withDuration: 0.35) {
                     self.daysControlView.alpha = 0