How can I set message status for the specified message

[function2000]

For example, I am sending 5 messages, and found all 5 messages are not sent successfully, so I need to set undelivered for all these message, then I do like below:
chatController!.initialMessageList[0].setStatus = MessageStatus.undelivered;
chatController!.initialMessageList[1].setStatus = MessageStatus.undelivered;
chatController!.initialMessageList[2].setStatus = MessageStatus.undelivered;
chatController!.initialMessageList[3].setStatus = MessageStatus.undelivered;
chatController!.initialMessageList[4].setStatus = MessageStatus.undelivered;

But it looks only last one works. Can you please check?
Thanks a lot!