Trouble with Swift 3 - MSStickerBrowserView and scrollview? - ios

Question

Alright, I'm having some issues in Swift 3 while trying desperately to add an MSStickerBrowserView to a UIScrollview.
I'm working in a message extension app and have added my scrollview via storyboard (I usually make them programmatically but I thought it'd be easier with constraints). I have connected the scrollview as an outlet in my MessagesViewController script.
I need to add an MSStickerBrowser I have created as a subview of this scrollview, meaning the user would be able to scroll TO the browser view and then scroll through the actual browser.
This is how I create my browser view normally and add it to the view - when added to the view it all works as it should:
func createStickerBrowser() {
let controller = MSStickerBrowserViewController(stickerSize: .large)
addChildViewController(controller)
view.addSubview(controller.view)
controller.stickerBrowserView.backgroundColor = UIColor.gray
controller.stickerBrowserView.dataSource = self
//resize this programmatically later
view.topAnchor.constraint(equalTo: controller.view.topAnchor).isActive = true
view.bottomAnchor.constraint(equalTo: controller.view.bottomAnchor).isActive = true
view.leftAnchor.constraint(equalTo: controller.view.leftAnchor).isActive = true
view.rightAnchor.constraint(equalTo: controller.view.rightAnchor).isActive = true
}
I don't know a lot about MSStickerBrowsers because the tutorials have been limited, however I know this ties the browser's size to that of the changing Message VC and adds it as a normal subview.
I then tried logically to just add it as a subview of the scrollview instead:
let controller = MSStickerBrowserViewController(stickerSize: .large)
//controller.view.frame = CGRect(x: 0, y: 0, width: view.bounds.width, height: view.bounds.height * 0.5)
addChildViewController(controller)
scrollView.addSubview(controller.view)
controller.stickerBrowserView.backgroundColor = UIColor.gray
controller.stickerBrowserView.dataSource = self
//resize this programmatically later
scrollView.topAnchor.constraint(equalTo: controller.view.topAnchor).isActive = true
scrollView.bottomAnchor.constraint(equalTo: controller.view.bottomAnchor).isActive = true
scrollView.leftAnchor.constraint(equalTo: controller.view.leftAnchor).isActive = true
scrollView.rightAnchor.constraint(equalTo: controller.view.rightAnchor).isActive = true
I've tried several variations but no matter what the sticker browser view is nowhere. The scrollview is there, not the browser, and no errors on that are printed to the console.
This seems like it should be simple - what am I doing wrong?