UINavigationBar extension for setting and applying "looks" in one go.

UINavigationBar+Looks.swift

//
//  UINavigationbar+Looks.swift
//
//  License: MIT
//

import UIKit

/**
 Stores information about navigation bar looks.
 */
struct NavigationBarLooks {
    var backIndicatorImage: UIImage?
    var backIndicatatorTransitionImageMask: UIImage?
    var barStyle: UIBarStyle?
    var barTintColor: UIColor?
    var shadowImage: UIImage?
    var tintColor: UIColor?
    var translucent: Bool?
    var backgroundImageMetrics: [UIBarMetrics: UIImage?]?
    var titleVerticalPosition: [UIBarMetrics: CGFloat]?
    var titleTextAttributes: [String: AnyObject]?

    init(backIndicatorImage: UIImage? = nil,
         backIndicatatorTransitionImageMask: UIImage? = nil,
         barStyle: UIBarStyle = UIBarStyle.Default,
         barTintColor: UIColor? = nil,
         shadowImage: UIImage? = nil,
         tintColor: UIColor? = nil,
         translucent: Bool = false,
         backgroundImageMetrics: [UIBarMetrics: UIImage?]? = [:],
         titleVerticalPosition: [UIBarMetrics: CGFloat]? = [:],
         titleTextAttributes: [String: AnyObject]? = [:])
    {
        self.backIndicatorImage = backIndicatorImage
        self.backIndicatatorTransitionImageMask = backIndicatatorTransitionImageMask
        self.barStyle = barStyle
        self.barTintColor = barTintColor
        self.shadowImage = shadowImage
        self.tintColor = tintColor
        self.translucent = translucent
        self.backgroundImageMetrics = backgroundImageMetrics
        self.titleVerticalPosition = titleVerticalPosition
        self.titleTextAttributes = titleTextAttributes
    }
}

private var metrics = [UIBarMetrics.Default, UIBarMetrics.DefaultPrompt, UIBarMetrics.Compact, UIBarMetrics.CompactPrompt]

extension UINavigationBar {

    /**
     Set the looks of the current navigation bar using the given `NavigationBarLooks`.
     
     - Parameter looks: The ´NavigationBarLooks` struct to apply to the current navigation bar.
     */
    func setBarLooks(looks: NavigationBarLooks) {
        backIndicatorImage = looks.backIndicatorImage
        backIndicatorTransitionMaskImage = looks.backIndicatatorTransitionImageMask
        barStyle = looks.barStyle ?? .Default
        barTintColor = looks.barTintColor
        shadowImage = looks.shadowImage
        tintColor = looks.tintColor
        translucent = looks.translucent ?? false

        looks.backgroundImageMetrics?.forEach { [unowned self] (metric, image) in
            self.setBackgroundImage(image, forBarMetrics: metric)
        }

        looks.titleVerticalPosition?.forEach { [unowned self] (metric, position) in
            self.setTitleVerticalPositionAdjustment(position ?? 0, forBarMetrics: metric)
        }

        titleTextAttributes = looks.titleTextAttributes
    }

    /**
     Fetch the current bar looks.
     
     - Returns: A `NavigationBarLooks` struct with values representing the current navigation bar.
     */
    func currentBarLooks() -> NavigationBarLooks {
        var backgroundImageMetrics = [UIBarMetrics: UIImage?]()
        var titlePositions = [UIBarMetrics: CGFloat]()
        metrics.forEach {
            backgroundImageMetrics[$0] = self.backgroundImageForBarMetrics($0)
            titlePositions[$0] = self.titleVerticalPositionAdjustmentForBarMetrics($0)
        }

        return NavigationBarLooks(backIndicatorImage: self.backIndicatorImage,
                                  backIndicatatorTransitionImageMask: self.backIndicatorTransitionMaskImage,
                                  barStyle: self.barStyle,
                                  barTintColor: self.barTintColor,
                                  shadowImage: self.shadowImage,
                                  tintColor: self.tintColor,
                                  translucent: self.translucent,
                                  backgroundImageMetrics: backgroundImageMetrics,
                                  titleVerticalPosition: titlePositions,
                                  titleTextAttributes: self.titleTextAttributes)
    }
}

Useful when one pushed view controller requires other navigation bar looks. Get current looks in viewDidLoad. Then in viewWillDissappear reapply the previous looks.