- (void)tryToStartSound:(NSSound *)sound ofType:(UCC3AudioType)type {
  UCC3AssertMainThread;
  
  if (!self.ammActiveRecording) {
    CSULogDebug(@"Will try to play sound %p of type %@ on device %@ with volume %.2f", sound, [UCC3ValueToString stringWithUCC3AudioType:type], sound.playbackDeviceIdentifier, sound.volume);
    [sound setCurrentTime:0];
    if ([sound play]) {
      [self setNumberOfStartRetriesCount:0 forType:type];
      CSULogDebug(@"Successfully started sound %p of type %@", sound, [UCC3ValueToString stringWithUCC3AudioType:type]);
    } else {
      NSInteger currentRetries = [self numberOfStartRetriesForType:type];
      if (currentRetries < MAX_START_STOP_RETRIES) {
        CSULogWarn(@"Failed to start sound %p of type %@. Will retry", sound, [UCC3ValueToString stringWithUCC3AudioType:type]);
        UCC3DefineWeakSelf;
        
        NSBlockOperation *operation = [NSBlockOperation blockOperationWithBlock:^{
          UCC3DefineStrongSelf;
          [self setNumberOfStartRetriesCount:currentRetries+1 forType:type];
          [self tryToStartSound:sound ofType:type];
        }];
        
        [self.operationQueue performSelector:@selector(addOperation:) withObject:operation afterDelay:UCC3AudioHelperRetryDelay];
      } else {
        CSULogError(@"Gave up trying to start sound %p", sound);
        [self setNumberOfStartRetriesCount:0 forType:type];
        self.playbackStateForAudioTypeMap[@(type)] = @(NO);
      }
    }
  } else {
    self.playbackStateForAudioTypeMap[@(type)] = @(NO);
    CSULogWarn(@"Won't play sound of type %@ due to active AMM recording", [UCC3ValueToString stringWithUCC3AudioType:type]);
  }
}

It is called as below :

UCC3DefineWeakSelf;
  [self.operationQueue addOperationWithBlock:^{
    UCC3DefineStrongSelf;
    [self tryToStartSound:sound ofType:type];
  }];

Definition of UCC3DefineWeakSelf as below 
#define UCC3DefineWeakSelf __weak typeof(self) weakSelf = self