Fix facebook#8615: NetInfo.isConnected for iOS

Summary:
This is fixing facebook#8615. The problem was that, on initialization, the `_connectionType` variable was still set to its default value of `RCTConnectionTypeUnknown`. The exposed API method did nothing to determine this unless a subscription had be established and then the method would simply return the last reported value. Instead, the exposed oneshot API call now actually checks the connection status through the same methods as the subscription and updates RCTNetInfo’s values before returning.

In order to avoid reporting events without a subscription, a flag is set and unset on calls to start/stopObserving.

- start app
- observe the (in)correct reporting of the manual status
- change network status to offline
- press refresh
- observe the manual fetch
- start subscription
- change network status to online
- press refresh to show that the manual refresh works (only now working for current RN version)
- change network status to offline
- stop subscription
- change network status to online
- press refresh to show manual refresh does(n't) work without subscription
- start subscription to show it updates to current

Current Behavior: https://drive.google.com/file/d/1Ods6HORgp_vfm1mQVjGwhtH1D7issxjo/view?usp=sharing
Fixed Behavior: https://drive.google.com/file/d/11H1UOF33LeMGvXEOoapU62ARDSb7qoYv/view?usp=sharing

[IOS] [BUGFIX] [Libraries\Network\RCTNetInfo.m] - Fixed facebook#8615, `iOS: NetInfo.isConnected returns always false`, by decoupling the fetch from the status of the subscription.
Closes facebook#17397

Differential Revision: D7102771

Pulled By: hramos

fbshipit-source-id: ea11eb0b1a7ca641fc43da2fe172cf7b2597de4a

Author: alburdette619

Libraries/Network/RCTNetInfo.m

@@ -41,13 +41,69 @@ @implementation RCTNetInfo
   NSString *_effectiveConnectionType;
   NSString *_statusDeprecated;
   NSString *_host;
+  BOOL _isObserving;
 }
 
 RCT_EXPORT_MODULE()
 
 static void RCTReachabilityCallback(__unused SCNetworkReachabilityRef target, SCNetworkReachabilityFlags flags, void *info)
 {
   RCTNetInfo *self = (__bridge id)info;
+  if ([self setReachabilityStatus:flags] && self->_isObserving) {
+    [self sendEventWithName:@"networkStatusDidChange" body:@{@"connectionType": self->_connectionType,
+                                                             @"effectiveConnectionType": self->_effectiveConnectionType,
+                                                             @"network_info": self->_statusDeprecated}];
+  }
+}
+
+#pragma mark - Lifecycle
+
+- (instancetype)initWithHost:(NSString *)host
+{
+  RCTAssertParam(host);
+  RCTAssert(![host hasPrefix:@"http"], @"Host value should just contain the domain, not the URL scheme.");
+
+  if ((self = [self init])) {
+    _host = [host copy];
+  }
+  return self;
+}
+
+- (NSArray<NSString *> *)supportedEvents
+{
+  return @[@"networkStatusDidChange"];
+}
+
+- (void)startObserving
+{
+  _isObserving = YES;
+  _connectionType = RCTConnectionTypeUnknown;
+  _effectiveConnectionType = RCTEffectiveConnectionTypeUnknown;
+  _statusDeprecated = RCTReachabilityStateUnknown;
+  _reachability = [self getReachabilityRef];
+}
+
+- (void)stopObserving
+{
+  _isObserving = NO;
+  if (_reachability) {
+    SCNetworkReachabilityUnscheduleFromRunLoop(_reachability, CFRunLoopGetMain(), kCFRunLoopCommonModes);
+    CFRelease(_reachability);
+  }
+}
+
+- (SCNetworkReachabilityRef)getReachabilityRef
+{
+  SCNetworkReachabilityRef reachability = SCNetworkReachabilityCreateWithName(kCFAllocatorDefault, _host.UTF8String ?: "apple.com");
+  SCNetworkReachabilityContext context = { 0, ( __bridge void *)self, NULL, NULL, NULL };
+  SCNetworkReachabilitySetCallback(reachability, RCTReachabilityCallback, &context);
+  SCNetworkReachabilityScheduleWithRunLoop(reachability, CFRunLoopGetMain(), kCFRunLoopCommonModes);
+    
+  return reachability;
+}
+
+- (BOOL)setReachabilityStatus:(SCNetworkReachabilityFlags)flags
+{
   NSString *connectionType = RCTConnectionTypeUnknown;
   NSString *effectiveConnectionType = RCTEffectiveConnectionTypeUnknown;
   NSString *status = RCTReachabilityStateUnknown;
@@ -96,54 +152,19 @@ static void RCTReachabilityCallback(__unused SCNetworkReachabilityRef target, SC
     self->_connectionType = connectionType;
     self->_effectiveConnectionType = effectiveConnectionType;
     self->_statusDeprecated = status;
-    [self sendEventWithName:@"networkStatusDidChange" body:@{@"connectionType": connectionType,
-                                                             @"effectiveConnectionType": effectiveConnectionType,
-                                                             @"network_info": status}];
-  }
-}
-
-#pragma mark - Lifecycle
-
-- (instancetype)initWithHost:(NSString *)host
-{
-  RCTAssertParam(host);
-  RCTAssert(![host hasPrefix:@"http"], @"Host value should just contain the domain, not the URL scheme.");
-
-  if ((self = [self init])) {
-    _host = [host copy];
-  }
-  return self;
-}
-
-- (NSArray<NSString *> *)supportedEvents
-{
-  return @[@"networkStatusDidChange"];
-}
-
-- (void)startObserving
-{
-  _connectionType = RCTConnectionTypeUnknown;
-  _effectiveConnectionType = RCTEffectiveConnectionTypeUnknown;
-  _statusDeprecated = RCTReachabilityStateUnknown;
-  _reachability = SCNetworkReachabilityCreateWithName(kCFAllocatorDefault, _host.UTF8String ?: "apple.com");
-  SCNetworkReachabilityContext context = { 0, ( __bridge void *)self, NULL, NULL, NULL };
-  SCNetworkReachabilitySetCallback(_reachability, RCTReachabilityCallback, &context);
-  SCNetworkReachabilityScheduleWithRunLoop(_reachability, CFRunLoopGetMain(), kCFRunLoopCommonModes);
-}
-
-- (void)stopObserving
-{
-  if (_reachability) {
-    SCNetworkReachabilityUnscheduleFromRunLoop(_reachability, CFRunLoopGetMain(), kCFRunLoopCommonModes);
-    CFRelease(_reachability);
+    return YES;
   }
+  
+  return NO;
 }
 
 #pragma mark - Public API
 
 RCT_EXPORT_METHOD(getCurrentConnectivity:(RCTPromiseResolveBlock)resolve
                   reject:(__unused RCTPromiseRejectBlock)reject)
 {
+  SCNetworkReachabilityRef reachability = [self getReachabilityRef];
+  CFRelease(reachability);
   resolve(@{@"connectionType": _connectionType ?: RCTConnectionTypeUnknown,
             @"effectiveConnectionType": _effectiveConnectionType ?: RCTEffectiveConnectionTypeUnknown,
             @"network_info": _statusDeprecated ?: RCTReachabilityStateUnknown});