fix(ios): Crash when rapidly switching pages #510

Author: doug-lessen

ios/ReactNativePageView.h

@@ -24,7 +24,7 @@ NS_ASSUME_NONNULL_BEGIN
 @property(nonatomic) BOOL overdrag;
 @property(nonatomic) NSString* layoutDirection;
 @property(nonatomic) CGRect previousBounds;
-
+@property(nonatomic, assign) BOOL animating;
 
 - (void)goTo:(NSInteger)index animated:(BOOL)animated;
 - (void)shouldScroll:(BOOL)scrollEnabled;

ios/ReactNativePageView.m

@@ -19,7 +19,7 @@ @interface ReactNativePageView () <UIPageViewControllerDataSource, UIPageViewCon
 @property(nonatomic, weak) UIView *currentView;
 
 @property(nonatomic, strong) NSHashTable<UIViewController *> *cachedControllers;
-@property (nonatomic, assign) CGPoint lastContentOffset;
+@property(nonatomic, assign) CGPoint lastContentOffset;
 
 - (void)goTo:(NSInteger)index animated:(BOOL)animated;
 - (void)shouldScroll:(BOOL)scrollEnabled;
@@ -181,6 +181,10 @@ - (void)setReactViewControllers:(NSInteger)index
     __weak ReactNativePageView *weakSelf = self;
     uint16_t coalescingKey = _coalescingKey++;
 
+    if (animated == YES) {
+        self.animating = YES;
+    }
+    
     [self.reactPageViewController setViewControllers:@[controller]
                                            direction:direction
                                             animated:animated
@@ -189,6 +193,10 @@ - (void)setReactViewControllers:(NSInteger)index
         strongSelf.currentIndex = index;
         strongSelf.currentView = controller.view;
 
+        if (finished) {
+            strongSelf.animating = NO;
+        }
+        
         if (strongSelf.eventDispatcher) {
             if (strongSelf.lastReportedIndex != strongSelf.currentIndex) {
                 if (shouldCallOnPageSelected) {

ios/ReactViewPagerManager.m

@@ -31,7 +31,9 @@ - (void) goToPage
             RCTLogError(@"Cannot find ReactNativePageView with tag #%@", reactTag);
             return;
         }
-        [view goTo:index.integerValue animated:animated];
+        if (!animated || !view.animating) {
+            [view goTo:index.integerValue animated:animated];
+        }
     }];
 }