expose flush on RCTWebSocketModule to close all open websockets synchronously (#14)

* expose `flush` on RCTWebSocketModule to close all open websockets synchronously

add log statement back

* simplify code

* simplify even more

* change comment

Author: nealmanaktola

Libraries/WebSocket/RCTSRWebSocket.h

@@ -80,6 +80,8 @@ extern NSString *const RCTSRHTTPResponseErrorKey;
 - (void)open;
 
 - (void)close;
+- (void)flush;
+
 - (void)closeWithCode:(NSInteger)code reason:(NSString *)reason;
 
 // Send a UTF8 String or Data.

Libraries/WebSocket/RCTSRWebSocket.m

@@ -549,6 +549,13 @@ - (void)unscheduleFromRunLoop:(NSRunLoop *)aRunLoop forMode:(NSString *)mode
   [_scheduledRunloops removeObject:@[aRunLoop, mode]];
 }
 
+- (void)flush
+{
+    // By queueing an empty block, all blocks queued before
+    // need to finish executing as this is a serial queue
+    dispatch_sync(_workQueue, ^{});
+}
+
 - (void)close
 {
   [self closeWithCode:RCTSRStatusCodeNormal reason:nil];

React/CoreModules/RCTWebSocketModule.h

@@ -24,6 +24,9 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (void)sendData:(NSData *)data forSocketID:(nonnull NSNumber *)socketID;
 
+// Blocking call that waits until there are no more remaining actions on the queue
+- (void)flush;
+
 @end
 
 @interface RCTBridge (RCTWebSocketModule)

React/CoreModules/RCTWebSocketModule.mm

@@ -51,6 +51,14 @@ - (NSArray *)supportedEvents
   return @[ @"websocketMessage", @"websocketOpen", @"websocketFailed", @"websocketClosed" ];
 }
 
+
+- (void)flush
+{
+  for (RCTSRWebSocket *socket in _sockets.allValues) {
+    [socket flush];
+  }
+}
+
 - (void)invalidate
 {
   [super invalidate];