Handle viewWillTransitionToSize across all `UIViewController`s

uvc_swizzle.swift

//  UIViewController+BackgroundStatusBar.swift
//  hailadoc-ios
//
//  Created by Gabriele Petronella on 7/16/15.
//  Copyright (c) 2015 buildo. All rights reserved.
//

import Foundation

extension UIViewController {
  public override class func initialize() {
    struct Static {
      static var token: dispatch_once_t = 0
    }

    // make sure this isn't a subclass
    if self !== UIViewController.self {
      return
    }

    dispatch_once(&Static.token) {
      let originalSelector = Selector("viewWillTransitionToSize:withTransitionCoordinator:")
      let swizzledSelector = Selector("hd_viewWillTransitionToSize:withTransitionCoordinator:")

      let originalMethod = class_getInstanceMethod(self, originalSelector)
      let swizzledMethod = class_getInstanceMethod(self, swizzledSelector)

      let didAddMethod = class_addMethod(self, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod))

      if didAddMethod {
        class_replaceMethod(self, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod))
      } else {
        method_exchangeImplementations(originalMethod, swizzledMethod);
      }
    }
  }

 func hd_viewWillTransitionToSize(size: CGSize, withTransitionCoordinator coordinator: UIViewControllerTransitionCoordinator) {
    self.hd_viewWillTransitionToSize(size, withTransitionCoordinator: coordinator)
    let isPortrait = size.width < size.height
    if let appDelegate = UIApplication.sharedApplication().delegate as? AppDelegate {
      UIView.animateWithDuration(0.3) {
        appDelegate.statusBarBackground.alpha = isPortrait ? 1 : 0
      }
    }
  }
}