Today we're back at it again with our YouTube application tutorial. I'll show you how to implement a couple of neat tricks in this video. First, we'll learn how to swipe away the navigation bar with a hidesBarsOnSwipe property. Next, we'll add a little horizontal slider bar using some iOS 9 anchor constraints to our menu bar. I'll then show you how to apply animation to this bar as you select different menu icons. Finally, we'll learn how to use completion blocks to abstract and clean out our controller code.

!codebreak <div class='filename'>HomeController.swift</div> !codebreak !syntax-highlight class HomeController: UICollectionViewController, UICollectionViewDelegateFlowLayout { var videos: [Video]? func fetchVideos() { ApiService.sharedInstance.fetchVideos { (videos: [Video]) in self.videos = videos self.collectionView?.reloadData() } } //... private func setupMenuBar() { navigationController?.hidesBarsOnSwipe = true let redView = UIView() redView.backgroundColor = UIColor.rgb(230, green: 32, blue: 31) view.addSubview(redView) view.addConstraintsWithFormat("H:|[v0]|", views: redView) view.addConstraintsWithFormat("V:[v0(50)]", views: redView) view.addSubview(menuBar) view.addConstraintsWithFormat("H:|[v0]|", views: menuBar) view.addConstraintsWithFormat("V:[v0(50)]", views: menuBar) menuBar.topAnchor.constraintEqualToAnchor(topLayoutGuide.bottomAnchor).active = true } //... } !codebreak <div class='filename'>MenuBar.swift</div> !codebreak !syntax-highlight class MenuBar: UIView, UICollectionViewDataSource, UICollectionViewDelegate, UICollectionViewDelegateFlowLayout { //... var horizontalBarLeftAnchorConstraint: NSLayoutConstraint? func setupHorizontalBar() { let horizontalBarView = UIView() horizontalBarView.backgroundColor = UIColor(white: 0.95, alpha: 1) horizontalBarView.translatesAutoresizingMaskIntoConstraints = false addSubview(horizontalBarView) //old school frame way of doing things // horizontalBarView.frame = CGRectMake(<#T##x: CGFloat##CGFloat#>, <#T##y: CGFloat##CGFloat#>, <#T##width: CGFloat##CGFloat#>, <#T##height: CGFloat##CGFloat#>) //new school way of laying out our views //in ios9 //need x, y, width, height constraints horizontalBarLeftAnchorConstraint = horizontalBarView.leftAnchor.constraintEqualToAnchor(self.leftAnchor) horizontalBarLeftAnchorConstraint?.active = true horizontalBarView.bottomAnchor.constraintEqualToAnchor(self.bottomAnchor).active = true horizontalBarView.widthAnchor.constraintEqualToAnchor(self.widthAnchor, multiplier: 1/4).active = true horizontalBarView.heightAnchor.constraintEqualToConstant(4).active = true } func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) { print(indexPath.item) let x = CGFloat(indexPath.item) * frame.width / 4 horizontalBarLeftAnchorConstraint?.constant = x UIView.animateWithDuration(0.75, delay: 0, usingSpringWithDamping: 1, initialSpringVelocity: 1, options: .CurveEaseOut, animations: { self.layoutIfNeeded() }, completion: nil) } //... } !codebreak <div class='filename'>ApiService.swift</div> !codebreak !syntax-highlight class ApiService: NSObject { static let sharedInstance = ApiService() func fetchVideos(completion: ([Video]) -> ()) { let url = NSURL(string: "https://s3-us-west-2.amazonaws.com/youtubeassets/home.json") NSURLSession.sharedSession().dataTaskWithURL(url!) { (data, response, error) in if error != nil { print(error) return } do { let json = try NSJSONSerialization.JSONObjectWithData(data!, options: .MutableContainers) var videos = [Video]() for dictionary in json as! [[String: AnyObject]] { let video = Video() video.title = dictionary["title"] as? String video.thumbnailImageName = dictionary["thumbnail_image_name"] as? String let channelDictionary = dictionary["channel"] as! [String: AnyObject] let channel = Channel() channel.name = channelDictionary["name"] as? String channel.profileImageName = channelDictionary["profile_image_name"] as? String video.channel = channel videos.append(video) } dispatch_async(dispatch_get_main_queue(), { completion(videos) }) } catch let jsonError { print(jsonError) } }.resume() } }