Simplified summary of NibReplaceable taken from https://github.com/BareFeetWare/BFWControls

NibReplaceable.swift

class NibView: UIView, NibReplaceable {
    
    open override func awakeAfter(using coder: NSCoder) -> Any? {
        guard subviews.isEmpty,
            let nibView = replacedByNibView()
            else { return self }
        return nibView
    }
    
}

public protocol NibReplaceable where Self: UIView {}

public extension NibReplaceable {
    
    public func replacedByNibView() -> Self? {
        let nibView = type(of: self).nibView()
        nibView?.copyProperties(from: self)
        nibView?.copyConstraints(from: self)
        return nibView
    }
    
    static func nibView() -> Self? {
        guard let nibViews = Bundle(for: self).loadNibNamed(nibName, owner: nil, options: nil),
            let nibView = nibViews.first(where: { type(of: $0) == self } ) as? Self
            else {
                fatalError("\(#function) Could not find an instance of class \(self) in \(nibName) xib")
        }
        return nibView
    }
    
    static var nibName: String {
        return String(describing: self)
    }

}