Nib.swift

import UIKit
import PureLayout

extension UINib {

    func instantiateWithOwner<T: AnyObject>(owner: AnyObject?, options: [NSObject : AnyObject]? = nil, type: T.Type) -> T {
        let objs = self.instantiateWithOwner(owner, options: options)
        return objs.findFirst { $0 is T } as! T
    }

}

protocol HasNib: AnyObject {

    static var nib: UINib { get }

}

extension HasNib {

    static var nib: UINib {
        return UINib(nibName: typeName(Self), bundle: NSBundle(forClass: Self.self))
    }

}

// MARK: - NibObject

protocol NibObject: HasNib {

    static func loadFromNib(owner: AnyObject?) -> Self

}

extension NibObject {

    static func loadFromNib(owner: AnyObject? = nil) -> Self {
        return nib.instantiateWithOwner(owner, type: Self.self)
    }

}

// MARK: - NibOwner

protocol NibOwner: HasNib {

    typealias NibContentClass

    func loadContentFromNib()
    func installContent(content: NibContentClass) // Template method.

}

extension NibOwner where NibContentClass: AnyObject {

    /**
     * The typical usage would be as follows.
     *
     *     override init(frame: CGRect) {
     *         super.init(frame: frame)
     *         loadContentFromNib()
     *     }
     *
     *     required init?(coder decoder: NSCoder) {
     *         super.init(coder: decoder)
     *         loadContentFromNib()
     *     }
     */
    func loadContentFromNib() {
        let content = Self.nib.instantiateWithOwner(self, options: nil, type: NibContentClass.self)
        installContent(content)
    }

}

extension NibOwner where Self: UIView, NibContentClass: UIView {

    func installContent(content: NibContentClass) {
        addSubview(content)
        content.autoPinEdgesToSuperviewEdges()
    }

}