ios: limit event queue

Author: arnaud-roland

ios/RNBatchEventDispatcher.m

@@ -1,11 +1,14 @@
 # import "RNBatchEventDispatcher.h"
-
+# define MAX_QUEUE_SIZE 5
 @implementation RNBatchEventDispatcher {
 
+    /// Whether NativeModule is ready or not
     BOOL _moduleIsReady;
 
+    /// Event queue
     NSMutableArray<RNBatchEvent*>* _events;
 
+    /// Block to send event from RNBatch
     void (^_sendBlock)(RNBatchEvent *_Nonnull event);
 }
 
@@ -17,53 +20,69 @@ -(instancetype)init {
     return self;
 }
 
+/// Set event sender block
 -(void)setSendBlock:(void (^)(RNBatchEvent* event))callback {
     _sendBlock = callback;
-    if(_sendBlock != nil) {
+    if (_sendBlock != nil) {
         [self dequeueEvents];
     }
 }
 
+/// Set native module is ready
 - (void)setModuleIsReady:(BOOL)ready {
     _moduleIsReady = ready;
 }
 
+/// Send an event to the Js bridge throught the block
+- (void)sendEvent:(RNBatchEvent*)event {
+    if (_sendBlock != nil) {
+        _sendBlock(event);
+    }
+}
 
-- (void)dequeueEvents {
-    if(_sendBlock == nil) {
-        return;
+/// Put an event in queue
+- (void)queueEvent:(RNBatchEvent*)event {
+    @synchronized(_events) {
+        if ([_events count] >= MAX_QUEUE_SIZE) {
+            [_events removeAllObjects];
+        }
+        [_events addObject:event];
     }
+}
+
+/// Dequeue all events
+- (void)dequeueEvents {
     @synchronized(_events) {
+        if ([_events count] == 0) {
+            return;
+        }
         NSArray *enqueuedEvents = [_events copy];
         [_events removeAllObjects];
-
         for (RNBatchEvent *event in enqueuedEvents) {
-            _sendBlock(event);
+            [self sendEvent:event];
         }
     }
 }
 
+/// Batch event dispatcher callback
 - (void)dispatchEventWithType:(BatchEventDispatcherType)type
                       payload:(nonnull id<BatchEventDispatcherPayload>)payload {
 
-    if (_moduleIsReady && _sendBlock == nil) {
-        // RN Module is ready but no listener registered
-        // not queuing up events
-        return;
-    }
+
     NSString* eventName = [RNBatchEventDispatcher mapBatchEventDispatcherTypeToRNEvent:type];
     if (eventName != nil) {
         RNBatchEvent* event = [[RNBatchEvent alloc] initWithName:eventName andBody:[self dictionaryWithEventDispatcherPayload:payload]];
-        @synchronized(_events) {
-            [_events addObject:event];
-        }
-        if (_sendBlock != nil) {
-            [self dequeueEvents];
+        if (!_moduleIsReady || _sendBlock == nil) {
+            NSLog(@"RNBatch: Module is not ready or no listener registered. Queueing event.");
+            [self queueEvent:event];
+            return;
         }
+        [self sendEvent:event];
     }
 }
 
-+ (nullable NSString *) mapBatchEventDispatcherTypeToRNEvent:(BatchEventDispatcherType)type {
+/// Mapping function
++ (nullable NSString *)mapBatchEventDispatcherTypeToRNEvent:(BatchEventDispatcherType)type {
     switch (type) {
         case BatchEventDispatcherTypeNotificationOpen:
             return @"notification_open";
@@ -82,6 +101,7 @@ + (nullable NSString *) mapBatchEventDispatcherTypeToRNEvent:(BatchEventDispatch
     }
 }
 
+/// Build payload event
 - (NSDictionary*) dictionaryWithEventDispatcherPayload:(id<BatchEventDispatcherPayload>)payload
 {
     NSMutableDictionary *output = [NSMutableDictionary dictionaryWithDictionary:@{
@@ -120,4 +140,4 @@ - (nonnull instancetype)initWithName:(nonnull NSString *)name andBody:(nullable
     return self;
 }
 
-@end
+@end