How to add a UIView on top of MessageKit's messagesCollectionView

If you want to have some sort of floating view above the messagesCollectionView, then you can just add it as a subview to the MessagesViewControler's view, just make sure to do it after you've called super.viewDidLoad() because that's where MessageKit adds the collectionView as a subview so if you add it before then, then your view will be behind the collectionView and won't appear. To prevent the cells overlapping with your view, you can use messagesCollectionView.contentInset property to add padding to either the top or bottom if your view is floating there, so that the user can still scroll to all of the messages. Something like this:

    override func viewDidLoad() {
        super.viewDidLoad()
        let subview = UIView()
        view.addSubview(subview)
        // Either add constraints or set the frame manually
        // ...
        // Set the contentInset if you want to prevent the messages from overlapping your view
        messagesCollectionView.contentInset.top = 10 // For example, if your view was stickied to the top and was height 10px
    }

Another route you could go is to have a parent view controller where you add the MessagesViewController as a child VC to the parent, and then size and layout the messagesCollectionView how you want. You can see an example of this in the MessageKit example app, in the MessageContainerController class: https://github.com/MessageKit/MessageKit/blob/master/Example/Sources/View%20Controllers/MessageContainerController.swift