fix(iOS): Xcode issues and warnings (no functionality changes) (#860)

* Fix Xcode warnings (enums, whitespace, string literals)

* Add nullability notations

ios/RNCWebView.h

 
 @protocol RNCWebViewDelegate <NSObject>
 
-- (BOOL)webView:(RNCWebView *)webView
-   shouldStartLoadForRequest:(NSMutableDictionary<NSString *, id> *)request
-   withCallback:(RCTDirectEventBlock)callback;
+- (BOOL)webView:(RNCWebView *_Nonnull)webView
+   shouldStartLoadForRequest:(NSMutableDictionary<NSString *, id> *_Nonnull)request
+   withCallback:(RCTDirectEventBlock _Nonnull)callback;
 
 @end
 
 @interface RNCWebView : RCTView
 
-@property (nonatomic, weak) id<RNCWebViewDelegate> delegate;
-@property (nonatomic, copy) NSDictionary *source;
+@property (nonatomic, weak) id<RNCWebViewDelegate> _Nullable delegate;
+@property (nonatomic, copy) NSDictionary * _Nullable source;
 @property (nonatomic, assign) BOOL messagingEnabled;
-@property (nonatomic, copy) NSString *injectedJavaScript;
+@property (nonatomic, copy) NSString * _Nullable injectedJavaScript;
 @property (nonatomic, assign) BOOL scrollEnabled;
 @property (nonatomic, assign) BOOL sharedCookiesEnabled;
 @property (nonatomic, assign) BOOL pagingEnabled;
 @property (nonatomic, assign) BOOL allowsBackForwardNavigationGestures;
 @property (nonatomic, assign) BOOL incognito;
 @property (nonatomic, assign) BOOL useSharedProcessPool;
-@property (nonatomic, copy) NSString *userAgent;
-@property (nonatomic, copy) NSString *applicationNameForUserAgent;
+@property (nonatomic, copy) NSString * _Nullable userAgent;
+@property (nonatomic, copy) NSString * _Nullable applicationNameForUserAgent;
 @property (nonatomic, assign) BOOL cacheEnabled;
 @property (nonatomic, assign) BOOL javaScriptEnabled;
 @property (nonatomic, assign) BOOL allowsLinkPreview;
 @property (nonatomic, assign) BOOL showsHorizontalScrollIndicator;
 @property (nonatomic, assign) BOOL showsVerticalScrollIndicator;
 @property (nonatomic, assign) BOOL directionalLockEnabled;
-@property (nonatomic, copy) NSString *allowingReadAccessToURL;
+@property (nonatomic, copy) NSString * _Nullable allowingReadAccessToURL;
 
 + (void)setClientAuthenticationCredential:(nullable NSURLCredential*)credential;
 + (void)setCustomCertificatesForHost:(nullable NSDictionary *)certificates;
-- (void)postMessage:(NSString *)message;
-- (void)injectJavaScript:(NSString *)script;
+- (void)postMessage:(NSString *_Nullable)message;
+- (void)injectJavaScript:(NSString *_Nullable)script;
 - (void)goForward;
 - (void)goBack;
 - (void)reload;

ios/RNCWebView.m

   } else {
     _isFullScreenVideoOpen = NO;
     RCTUnsafeExecuteOnMainQueueSync(^{
-      [RCTSharedApplication() setStatusBarHidden:_savedStatusBarHidden animated:YES];
-      [RCTSharedApplication() setStatusBarStyle:_savedStatusBarStyle animated:YES];
+      [RCTSharedApplication() setStatusBarHidden:self->_savedStatusBarHidden animated:YES];
+      [RCTSharedApplication() setStatusBarStyle:self->_savedStatusBarStyle animated:YES];
     });
   }
 #pragma clang diagnostic pop
  * topViewController
  */
 -(UIViewController *)topViewController{
-   UIViewController *controller = [self topViewControllerWithRootViewController:[self getCurrentWindow].rootViewController];
-   return controller;
+    UIViewController *controller = [self topViewControllerWithRootViewController:[self getCurrentWindow].rootViewController];
+    return controller;
 }
 
 /**
     if (![self.delegate webView:self
       shouldStartLoadForRequest:event
                    withCallback:_onShouldStartLoadWithRequest]) {
-      decisionHandler(WKNavigationResponsePolicyCancel);
+      decisionHandler(WKNavigationActionPolicyCancel);
       return;
     }
   }
   }
 
   // Allow all navigation by default
-  decisionHandler(WKNavigationResponsePolicyAllow);
+  decisionHandler(WKNavigationActionPolicyAllow);
 }
 
 /**
       callback([NSString stringWithFormat:@"%@", result]);
     }
     if (error != nil) {
-      RCTLogWarn([NSString stringWithFormat:@"Error evaluating injectedJavaScript: This is possibly due to an unsupported return type. Try adding true to the end of your injectedJavaScript string. %@", error]);
+      RCTLogWarn(@"%@", [NSString stringWithFormat:@"Error evaluating injectedJavaScript: This is possibly due to an unsupported return type. Try adding true to the end of your injectedJavaScript string. %@", error]);
     }
   }];
 }