NibLoadableView

NibLoadable.swift

import UIKit

protocol NibLoadable {
    func setupFromXib()
}

// This extension loads a .xib file with the same filename as the class name
// i.e. `class FoobarHeaderView` -> loads FoobarHeaderView.xib
extension NibLoadable where Self: UIView {
    func setupFromXib() {
        // load the root UIView (i.e. root subview layer of the xib)
        let bundle = NSBundle(forClass: self.dynamicType)
        let className = NSStringFromClass(self.dynamicType).componentsSeparatedByString(".").last!
        let nib = UINib(nibName: className, bundle: bundle)
        
        // reminder: instantiating with `owner: self` takes care of hooking up
        // all the IBOutlets from the nib, to this class
        let rootView = nib.instantiateWithOwner(self, options: nil)[0] as! UIView
        
        // setup that view's geometry
        rootView.frame = bounds
        rootView.autoresizingMask = [UIViewAutoresizing.FlexibleWidth, UIViewAutoresizing.FlexibleHeight]
        
        // add that view to myself
        addSubview(rootView)
    }
}

NibLoadableView.swift

import UIKit

// Subclasses:
// When reimplementing `commonInit`, call the super implementation, first.

class NibLoadableView: UIView, NibLoadable {

    override init(frame: CGRect) {
        super.init(frame: frame)
        commonInit()
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        commonInit()
    }
    
    func commonInit() {
        setupFromXib()
    }
}