diff --git a/React/Views/RCTComponentData.m b/React/Views/RCTComponentData.m
index d7738b05290a73..46eb77a8a3665b 100644
--- a/React/Views/RCTComponentData.m
+++ b/React/Views/RCTComponentData.m
@@ -234,9 +234,8 @@ - (RCTPropBlock)propBlockForKey:(NSString *)name
             setterBlock = ^(id target, id json) { \
               if (json) { \
                 if (!setDefaultValue && target) { \
-                  if ([target respondsToSelector:getter]) { \
-                    defaultValue = get(target, getter); \
-                  } \
+                  RCTAssert([target respondsToSelector:getter], @"prop getter does not exist: %@", NSStringFromSelector(getter)); \
+                  defaultValue = get(target, getter); \
                   setDefaultValue = YES; \
                 } \
                 set(target, setter, convert([RCTConvert class], type, json)); \
diff --git a/React/Views/RCTShadowView.m b/React/Views/RCTShadowView.m
index da9a8a83a62459..a3bac95eb5a294 100644
--- a/React/Views/RCTShadowView.m
+++ b/React/Views/RCTShadowView.m
@@ -636,6 +636,11 @@ - (void)setFlex:(float)value
   YGNodeStyleSetFlex(_cssNode, value);
 }
 
+- (float)flex
+{
+  return YGNodeStyleGetFlex(_cssNode);
+}
+
 - (void)setFlexBasis:(YGValue)value
 {
   RCT_SET_YGVALUE(value, YGNodeStyleSetFlexBasis, _cssNode);
diff --git a/React/Views/RCTSwitch.m b/React/Views/RCTSwitch.m
index 6c4e2856495931..a14cf7051c9669 100644
--- a/React/Views/RCTSwitch.m
+++ b/React/Views/RCTSwitch.m
@@ -14,6 +14,12 @@
 
 @implementation RCTSwitch
 
+// `on` is a component prop, so we must expose symmetrical `on` and `setOn` methods.
+// UIView breaks convention with the name `isOn`, so we simply forward.
+- (BOOL)on {
+  return [self isOn];
+}
+
 - (void)setOn:(BOOL)on animated:(BOOL)animated {
   _wasOn = on;
   [super setOn:on animated:animated];
diff --git a/React/Views/RCTTabBar.m b/React/Views/RCTTabBar.m
index e6fa3490c85cdb..b53b86cba4c219 100644
--- a/React/Views/RCTTabBar.m
+++ b/React/Views/RCTTabBar.m
@@ -149,6 +149,15 @@ - (void)setTranslucent:(BOOL)translucent {
   _tabController.tabBar.translucent = translucent;
 }
 
+- (UIColor *)unselectedItemTintColor {
+#if defined(__IPHONE_OS_VERSION_MAX_ALLOWED) && __IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_10_0
+  if ([_tabController.tabBar respondsToSelector:@selector(unselectedItemTintColor)]) {
+    return _tabController.tabBar.unselectedItemTintColor;
+  }
+#endif
+  return nil;
+}
+
 - (void)setUnselectedItemTintColor:(UIColor *)unselectedItemTintColor {
 #if defined(__IPHONE_OS_VERSION_MAX_ALLOWED) && __IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_10_0
   if ([_tabController.tabBar respondsToSelector:@selector(unselectedItemTintColor)]) {
diff --git a/ReactCommon/yoga/yoga/Yoga.c b/ReactCommon/yoga/yoga/Yoga.c
index a6dde07d56019c..799572f09e01e0 100644
--- a/ReactCommon/yoga/yoga/Yoga.c
+++ b/ReactCommon/yoga/yoga/Yoga.c
@@ -442,6 +442,10 @@ void YGNodeStyleSetFlex(const YGNodeRef node, const float flex) {
   }
 }
 
+float YGNodeStyleGetFlex(const YGNodeRef node) {
+  return node->style.flex;
+}
+
 #define YG_NODE_PROPERTY_IMPL(type, name, paramName, instanceName) \
   void YGNodeSet##name(const YGNodeRef node, type paramName) {     \
     node->instanceName = paramName;                                \
diff --git a/ReactCommon/yoga/yoga/Yoga.h b/ReactCommon/yoga/yoga/Yoga.h
index bf9bd3e894321d..eed58935405317 100644
--- a/ReactCommon/yoga/yoga/Yoga.h
+++ b/ReactCommon/yoga/yoga/Yoga.h
@@ -160,6 +160,7 @@ YG_NODE_STYLE_PROPERTY(YGOverflow, Overflow, overflow);
 YG_NODE_STYLE_PROPERTY(YGDisplay, Display, display);
 
 WIN_EXPORT void YGNodeStyleSetFlex(const YGNodeRef node, const float flex);
+WIN_EXPORT float YGNodeStyleGetFlex(const YGNodeRef node);
 YG_NODE_STYLE_PROPERTY(float, FlexGrow, flexGrow);
 YG_NODE_STYLE_PROPERTY(float, FlexShrink, flexShrink);
 YG_NODE_STYLE_PROPERTY_UNIT(YGValue, FlexBasis, flexBasis);