UIToolbar with a right-aligned "Done" button, for use as a keyboard accessory view

KeyboardAccessoryView.swift

lazy var accessoryToolbarWithDoneButton: UIToolbar = {

    let toolbar = UIToolbar(frame: CGRect.zero)
    //only needs to be flexible in the dimension(s) you want it to be
    //https://stackoverflow.com/questions/31822504/how-can-i-increase-the-height-of-an-inputaccessoryview
    toolbar.autoresizingMask = [.flexibleWidth, .flexibleHeight] 
    
    let leftSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil)
    let doneButton = UIBarButtonItem(barButtonSystemItem: .done, target: self, action: #selector(keyboardDoneButtonTapped(_:)))
    toolbar.items = [leftSpace, doneButton]
    
    return toolbar
}()

@objc func keyboardDoneButtonTapped(_ sender: UIBarButtonItem) {
    //resign first responder on the appropriate field
}