Don’t show app upgrade nag unless we are at rest in home view or registration view.

// FREEBIE

Signal/src/UIApplication+OWS.swift

@@ -9,8 +9,20 @@ extension UIApplication {
     var frontmostViewController: UIViewController? {
         let window = UIApplication.shared.keyWindow
         var viewController = window!.rootViewController
-        while viewController?.presentedViewController != nil {
-            viewController = viewController?.presentedViewController
+        
+        while true {
+            if let nextViewController = viewController?.presentedViewController {
+                viewController = nextViewController
+            } else if viewController is UINavigationController {
+                let navigationController = viewController as? UINavigationController
+                if let nextViewController = navigationController?.topViewController {
+                    viewController = nextViewController
+                } else {
+                    break
+                }
+            } else {
+                break
+            }
         }
 
         return viewController

Signal/src/util/AppUpdateNag.m

@@ -3,6 +3,8 @@
 //
 
 #import "AppUpdateNag.h"
+#import "RegistrationViewController.h"
+#import "Signal-Swift.h"
 #import <ATAppUpdater/ATAppUpdater.h>
 #import <SignalServiceKit/TSStorageManager.h>
 
@@ -55,6 +57,17 @@ NSString *const TSStorageManagerAppUpgradeNagDate = @"TSStorageManagerAppUpgrade
 
 - (void)showAppUpgradeNagIfNecessary
 {
+    // Only show nag if we are "at rest" in the home view or registration view without any
+    // alerts or dialogs showing.
+    UIViewController *frontmostViewController =
+    [UIApplication sharedApplication].frontmostViewController;
+    OWSAssert(frontmostViewController);
+    BOOL canPresent = ([frontmostViewController isKindOfClass:[SignalsViewController class]] ||
+                       [frontmostViewController isKindOfClass:[RegistrationViewController class]]);
+    if (!canPresent) {
+        return;
+    }
+    
     NSDate *lastNagDate = [[TSStorageManager sharedManager] dateForKey:TSStorageManagerAppUpgradeNagDate
                                                           inCollection:TSStorageManagerAppUpgradeNagCollection];
     const NSTimeInterval kMinute = 60.f;