ShowHideNavAndTab

//  Hiding NavBar and TabBar example
//  Created by Joel Kopelioff on 1/30/15.
//

import UIKit
import SVProgressHUD
import CoreData


class MyViewController: UIViewController, UITableViewDelegate, UITableViewDataSource, UIScrollViewDelegate {

	@IBOutlet weak var tableView: UITableView!

	// Bar showing/hiding on scroll
	
	var lastContentOffset:CGFloat?
	var showBars:Bool = true
	
	// Ususally goes in a constants file
	let DELEG = UIApplication.sharedApplication().delegate as AppDelegate
  ....
  
        //MARK: Status Bar toggle
  
	override func prefersStatusBarHidden() -> Bool {
		return !self.showBars
	}

	
	//MARK: ScrollView

	func scrollViewDidScroll(scrollView: UIScrollView) {

		let navHeight = self.navigationController?.navigationBar.frame.height

		if scrollView.contentOffset.y < 0 || 
		   scrollView.contentOffset.y >= scrollView.contentSize.height - scrollView.frame.size.height || 
		   navHeight == nil ||
			 scrollView.contentSize.height <= scrollView.frame.size.height + navHeight!
		{
			return
		}

		var show:Bool = true
		if self.lastContentOffset > scrollView.contentOffset.y {
			show = true
		} else if self.lastContentOffset < scrollView.contentOffset.y {
			show = false
		}

		self.lastContentOffset = scrollView.contentOffset.y;

		if self.showBars != show {
			self.showBars = show
			self.setNeedsStatusBarAppearanceUpdate()

			self.navigationController?.setNavigationBarHidden(!show, animated: true)
			self.setTabBarVisible(show, animated: true)
		}
	}

	//MARK: Tabbar Visibility

	func setTabBarVisible(visible:Bool, animated:Bool) {

		if DELEG.window?.rootViewController is UITabBarController {

			var tabBarController = DELEG.window?.rootViewController as UITabBarController

			//* This cannot be called before viewDidLayoutSubviews(), because the frame is not set before this time

			// bail if the current state matches the desired state
			if (tabBarIsVisible(tabBarController) == visible) { return }

			// get a frame calculation ready
			let frame = tabBarController.tabBar.frame
			let height = frame.size.height
			let offsetY = (visible ? -height : height)

			// zero duration means no animation
			let duration:NSTimeInterval = (animated ? 0.3 : 0.0)

			//  animate the tabBar
			UIView.animateWithDuration(duration, animations: { () -> Void in
				tabBarController.tabBar.frame = CGRectOffset(frame, 0, offsetY)
			})
		}
	}

	func tabBarIsVisible(tabBarController:UITabBarController) ->Bool {
		return tabBarController.tabBar.frame.origin.y < CGRectGetMaxY(DELEG.window!.frame)
	}
}