Allows for easily setting a theme on the navigation bar.

NavigationTheme.swift

//
//  NavigationTheme.swift
//
//  Created by James Valaitis on 13/04/2018.
//

import UIKit

//  MARK: Navigation Theme
/**
Encapsulates the information to theme a navigation controller.
*/
public struct NavigationTheme {
	//  MARK: Properties
	///	The text attributes for the navigation bar.
	let titleTextAttributes: [NSAttributedString.Key: Any]
	///	The color for the navigation bar.
	let barTintColor: UIColor
	///	The color for the buttons in the navigation bar.
	let tintColor: UIColor
	///	The image for the shadow below the navigation bar.
	let shadowImage: UIImage
	///	Whether or not the bar should be translucent.
	let isTranslucent: Bool
	///	The background image for the navigation bar.
	let backgroundImage: UIImage
}
//  MARK: Initialization
public extension NavigationTheme {
	init(attributes: [NSAttributedString.Key: Any], barColor: UIColor, tintColor: UIColor, shadowImage: UIImage = UIImage(), translucent: Bool = true, backgroundImage: UIImage = UIImage()) {
		self.init(titleTextAttributes: attributes, barTintColor: barColor, tintColor: tintColor, shadowImage: shadowImage, isTranslucent: translucent, backgroundImage: backgroundImage)
	}
}
//  MARK: Constants
public extension NavigationTheme {
	///	A transparent navigation bar with white buttons.
	static var transparentWhite: NavigationTheme { return NavigationTheme(attributes: [.font: UIFont(name: .avenirNextRegular, size:14.0)], barColor: .clear, tintColor: .white) }
}

//  MARK: UINavigationBar + NavigationTheme
public extension UINavigationBar {
	func apply(_ theme: NavigationTheme, withTransition fading: Bool = false, fadingTime time: CFTimeInterval = 0.25) {
		barTintColor = theme.barTintColor
		titleTextAttributes = theme.titleTextAttributes
		tintColor = theme.tintColor
		shadowImage = theme.shadowImage
		isTranslucent = theme.isTranslucent
		
		if fading {
			let transition = CATransition()
			transition.timingFunction = CAMediaTimingFunction(name: CAMediaTimingFunctionName.easeInEaseOut)
			transition.type = .fade
			transition.duration = time
			self.layer.add(transition, forKey: nil)
		}
		
		setBackgroundImage(theme.backgroundImage, for: UIBarMetrics.default)
	}
}