UIView.animate – Swift 3 – completion

You add it like this:

UIView.animate(withDuration: 0.25, delay: 0.0, options: [], animations: {
    self.drawerView?.frame = CGRect(x: 0, y: 0, width: (self.drawerView?.frame.size.width)!, height: (self.drawerView?.frame.size.height)!)
    self.contentView?.frame = CGRect(x: 200, y: 0, width: (self.contentView?.frame.size.width)!, height: (self.contentView?.frame.size.height)!)
}, completion: { (finished: Bool) in
    self.isOpen = true
})