Thread safe Antenna approach

gistfile1.m

- (void)addChannel:(id <AntennaChannel>)channel forName:(NSString *)name {
    dispatch_barrier_async(_channelsThreadQueue, ^{
      /**
       * Has this channel already been added?
       */
      if ([self channelExists:name]) {
        return;
      }

      NSDictionary *notifInfo   = @{AntennaChannelNotificationDictKey : name};
  
      self.channels[name] = channel;
  
      [[NSNotificationCenter defaultCenter] postNotificationName:AntennaChannelAddedNotification
                                                          object:nil
                                                        userInfo:notifInfo];
    });
}

- (void)removeChannelForName:(NSString *)name {
   dispatch_barrier_async(_channelsThreadQueue, ^{
      /**
       * Has this channel already been removed?
       */
      if (![self channelExists:name]) {
        return;
      }
  
      [self.channels removeObjectForKey:name];
  
      NSDictionary *notifInfo = @{AntennaChannelNotificationDictKey : name};
  
      [[NSNotificationCenter defaultCenter] postNotificationName:AntennaChannelRemovedNotification
                                                          object:nil
                                                        userInfo:notifInfo];
  });
}


- (id <AntennaChannel>)channelForName:(NSString *)name {

  id <AntennaChannel> channelObject = nil;
  
  dispatch_sync(_channelsThreadQueue, ^{
    channelObject = self.channels[name];
  });

  return channelObject;
}