How do you make the sender display name appear with JSQMessageViewController?

I have the following function that gets called for adding a message:

    func addMessage(text: String, displayName: String) {
        let message = JSQMessage(senderId: "tester", displayName: displayName, text: text)
        messages.append(message)

        finishReceivingMessage()

}

Then in this function

    override func collectionView(collectionView: JSQMessagesCollectionView!,
    messageDataForItemAtIndexPath indexPath: NSIndexPath!) -> JSQMessageData! {
        return messages[indexPath.item]
}

I return the message date for that indexPath. The message appears correctly but there is no display name.

I think you are missing the attributedTextForMessageBubbleTopLabelAtIndexPath should look something like this

 override func collectionView(collectionView: JSQMessagesCollectionView?, attributedTextForMessageBubbleTopLabelAtIndexPath indexPath: NSIndexPath!) -> NSAttributedString! {
    let message = messages[indexPath.item]
    switch message.senderId {
    case CURRENTUSERID:
        return nil
    default:
        guard let senderDisplayName = message.senderDisplayName else {
            assertionFailure()
            return nil
        }
        return NSAttributedString(string: senderDisplayName)
        
    }
}

Edit:

Also make sure you give the label a hight with this function

override func collectionView(collectionView: JSQMessagesCollectionView!, layout collectionViewLayout: JSQMessagesCollectionViewFlowLayout!, heightForMessageBubbleTopLabelAtIndexPath indexPath: NSIndexPath!) -> CGFloat {
   return 13 //or what ever height you want to give
}