IBOutlet properties nil after custom view loaded from xib

That’s expected, because the IBOutlet(s) are not assigned by the time the initializer is called.

Instead of calling commonInit() in init(coder:), do that in an override of awakeFromNib as follows:

// ...

required init(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
}

override func awakeFromNib() {
    super.awakeFromNib()

    commonInit()
}

// ...